Re: How to avoid certain directories when using os.walk?
En Fri, 30 Oct 2009 14:50:34 -0300, Sean DiZazzo half.ital...@gmail.com escribió: On Oct 29, 10:17 pm, Chris Rebert c...@rebertia.com wrote: On Thu, Oct 29, 2009 at 9:53 PM, Peng Yu pengyu...@gmail.com wrote: I don't see a way to avoid walking over directories of certain names with os.walk. For example, I don't want os.walk return files whose path include '/backup/'. Is there a way to do so? Otherwise, maybe I will have to make my own program. Thank you! Read the docs! (http://docs.python.org/library/os.html#os.walk): They even include a specific code example of how to skip unwanted subdirectories. You will run into problems however if you want to delete from a tree while ignoring certain named directories. Directories must be empty before they can be deleted, so you must use topdown=False, but to prune a search you must use topdown=True. At least I think that was the problem I had with my deletion script a while back. I'd say the problem is ill-defined in that case. You have to decide what to do with those non-empty directories that are non-empty because you explicitely skipped some subdirectories... -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: How can module determine its own path?
En Fri, 30 Oct 2009 20:40:59 -0300, Stef Mientki stef.mien...@gmail.com escribió: Robert Kern wrote: On 2009-10-30 12:19 PM, kj wrote: How can a module determine the path of the file that defines it? (Note that this is, in the general case, different from sys.argv[0].) __file__ but for modules launched with execfile, __file__ doesn't exists. Remember that execfile just executes the file contents, it does not create a new module nor interacts with the module management. modules launched with execfile has no meaning. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
How to get output of command called by os.system()?
I need to integrate shell program with python. I'm wondering if there is a way get the output of the shell program called by os.system(). Thank you! -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get output of command called by os.system()?
On Fri, Oct 30, 2009 at 11:09 PM, Peng Yu pengyu...@gmail.com wrote: I need to integrate shell program with python. I'm wondering if there is a way get the output of the shell program called by os.system(). You'd probably do better to use the `subprocess` module instead: http://docs.python.org/library/subprocess.html Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
How to get the realpath of a symbolic link?
Suppose that I have the following directory and files. I want to get
the canonical path of a file, a directory or a symbolic link.
For example, for 'b' below, I want to get its canonical path as
'/private/tmp/abspath/b'.
However, os.path.abspath('b') gives me '/private/tmp/abspath/b', but
os.path.abspath('/tmp/abspath/b') gives me '/tmp/abspath/b'.
The results are not the same. So, neither os.path.abspath or
os.path.realpath gives me what I want.
I'm wondering if there is a way to get the canonical path
'/private/tmp/abspath/b', no matter whether the argument is 'b' or
'/tmp/abspath/b'.
$./test.py
/private/tmp/abspath/a
/private/tmp/abspath/a
/private/tmp/abspath/a
/private/tmp/abspath/a
/private/tmp/abspath/a
/private/tmp/abspath/b
/tmp/abspath/a
/tmp/abspath/b
$cat test.py
#!/usr/bin/env python
import os.path
print os.path.realpath('a')
print os.path.realpath('b')
print os.path.realpath('/tmp/abspath/a')
print os.path.realpath('/tmp/abspath/b')
print os.path.abspath('a')
print os.path.abspath('b')
print os.path.abspath('/tmp/abspath/a')
print os.path.abspath('/tmp/abspath/b')
$pwd
/tmp/abspath
$gls -Rgtra
.:
total 8
-rw-r--r-- 1 wheel 0 2009-10-31 01:52 a
lrwxr-xr-x 1 wheel 1 2009-10-31 01:52 b - a
-rwx--x--x 1 wheel 312 2009-10-31 01:54 test.py
drwx-- 5 wheel 170 2009-10-31 01:54 .
drwxrwxrwt 23 wheel 782 2009-10-31 01:56 ..
$gls -lgtr /tmp
lrwxr-xr-x 1 admin 11 2009-05-21 04:28 /tmp - private/tmp
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Why do you use python?
What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? (because my resume says I know C/C++/Java)? -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
On Oct 31, 8:11 am, sk catchyouraak...@gmail.com wrote: What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? (because my resume says I know C/C++/Java)? I also know C/C++/Java so... I'd say that I can be much more productive in Python that in those other languages. I can do the same with , let's say, 5 lines of Python that with 15 or 20 lines of C/C++/Java (maybe a little less in Java), with much less errors. I can produce clear code, so it's easier to understand when other person will look at it. I can produce a prototype much faster I can focus more on the problem and less on the coding... I can make cross-platform code (well, also with Java) I would use it as much as possible, but specially for: * Complicated script-like actions, in spair of bash scripts, which it's great for simple , OS related operations, but to manage workflow it's sometimes confusing. * Rapid prototyping. Check ideas. * Tests automation I try to use Python as often as possible, as my default language, as I think I can't be more productive, which it's usually the most important parameter in software development. Of course, if there is a good reason not to use it, then it's not the adequate tool. But But I tend to ask myself Is there a reason for not using Python? instead of Is there a reason for using Python? -- http://mail.python.org/mailman/listinfo/python-list
Feedback desired on reworked ch 1 progr. intro (now Python 3.x, Windows)
Hi all! After my earlier feedback request a lot of you responded with constructive criticism and suggestions. As a result of that I've changed the text to be based on *Python 3.x* instead of 2.6+, and chapter 1 Getting started has grown from 9 pages to a whopping 11 pages! I would particularly like to thank the following persons (although of course I don't know whether any of them would recommend the old text, or the new text! :-) ), because they directly caused changes of the text: Chris Rebert, in [comp.lang.python] Ch 1 all batteries included - batteries included OS/X - Mac OS X (with a space, not a slash) implementation - distribution Eric Brunel, in [comp.lang.python] Ch 1 static type checking discussion yielding wrong impression ba...@freeuk.com, in [comp.lang.python] Ch 1 Unclear that Windows subsystems are not something to do with Python. Ethan Furman, in private communication Ch 1 Pointed out the renaming 2.6 Tkinter - 3.x tkinter Jon Clements, in [comp.lang.python] General Info about Python 3.x that let me switch to 3.x Plus, the person who suggested that I should mention the PSPad editor, but I forgot to note who that was (sorry). I hope this new version of ch 1 is, well, better, addresses some of the concerns raised? g url: http://preview.tinyurl.com/ProgrammingBookP3 Formats: PDF, text Now starting on ch 2, which with Python 3.x should become a lot cleaner... Cheers, - Alf -- http://mail.python.org/mailman/listinfo/python-list
Re: self.__dict__ tricks
On Friday, 30 October 2009 17:28:47 MRAB wrote: Wouldn't it be clearer if they were called dromedaryCase and BactrianCase? :-) Ogden Nash: The Camel has a single hump- The Dromedary, two; Or the other way around- I'm never sure. - Are You? - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: Sqlite3. Substitution of names in query.
In message mailman.2357.1256964121.2807.python-l...@python.org, Dennis Lee Bieber wrote: This way regular string interpolation operations (or whatever Python 3.x has replaced it with) are safe to construct the SQL, leaving only user supplied (or program generated) data values to be passed via the DB-API parameter system -- so that they are properly escaped and rendered safe. Mixing the two is another recipe for confusion and mistakes. -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
In message 6e603d9c-2be0-449c-9c3c- bab49e09e...@13g2000prl.googlegroups.com, Carl Banks wrote: It's not Python that's the issue. The issue is that if you have a module with a .dll extension, other programs could accidentally try to load that module instead of the intended dll, if the module is in the current directory or system path. Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Sat, 2009-10-31 at 21:32 +1300, Lawrence D'Oliveiro wrote: Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? I think as someone pointed out earlier, in Unix-like operating systems, a regular library's file name starts with lib, e.g. libcrypt.so. So this would not conflict with Python's crypt.so. But in Windows, they would both be named crypt.dll, for example (I'm halfway guessing since I don't have/use Windows). -- http://mail.python.org/mailman/listinfo/python-list
Re: Web development with Python 3.1
notmm uses Python 2.6 and will probably work just fine with Python 3000. The only reference to notmm that I could find in Google was this thread! I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do. -- Robert A. Heinlein Heinlein said that? It's been a long time since I've read Heinlein, and his quotes are as vivid as his books. -- Dotan Cohen http://what-is-what.com http://gibberish.co.il -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get output of command called by os.system()?
On Oct 30, 11:09 pm, Peng Yu pengyu...@gmail.com wrote:
I need to integrate shell program with python. I'm wondering if there
is a way get the output of the shell program called by os.system().
Thank you!
popen should do what your after. There are several modules that have
a popen method including os and subprocess. It will allow you to make
a system call similar to os.system, but it gives you pipe access, like
an open file, to the standard output and standard error if you use
subprocess.Popen. A simple example would be:
import subprocess
output = subprocess.Popen('pwd')
print('Present Working Directory is: ' + output.readline())
Hope that helps.
-John
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Re: datetime question
On Sat, 2009-10-31 at 10:08 +1100, Ben Finney wrote: The ‘datetime’ module focusses on individual date+time values (and the periods between them, with the ‘timedelta’ type). For querying the properties of the calendar, use the ‘calendar’ module. Yes, it would be nice if the ‘time’, ‘datetime’, and ‘calendar’ modules were all much more unified and consumed a common set of primitive date+time types. It's a wart, and fixing it would (unfortunately) probably require backward-incompatible API changes. But, supposedly, that's why we had Python3. -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
sk wrote: What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? (because my resume says I know C/C++/Java)? I would say where I can, where 'can' is depending on the problem, already implementations and requirements. On the other hand, when I go to a restaurant I usually don't tell the chef which brand of knives he has to prepare my meal with, even though I prefer Globals knives for my own use. -- MPH http://blog.dcuktec.com 'If consumed, best digested with added seasoning to own preference.' -- http://mail.python.org/mailman/listinfo/python-list
Re: datetime question
Albert Hopkins mar...@letterboxes.org writes: On Sat, 2009-10-31 at 10:08 +1100, Ben Finney wrote: Yes, it would be nice if the ‘time’, ‘datetime’, and ‘calendar’ modules were all much more unified and consumed a common set of primitive date+time types. It's a wart, and fixing it would (unfortunately) probably require backward-incompatible API changes. But, supposedly, that's why we had Python3. Fixing ‘time’, ‘datetime’, and ‘calendar’ was the reason for Python 3? No, it wasn't. Or perhaps you mean that any backward-incompatible change was a reason to have Python 3? Even more firmly no. The extent of changes was severely limited to make the transition from Python 2 to Python 3 as painless as feasible, while still meeting the goals of Python 3. -- \“Odious ideas are not entitled to hide from criticism behind | `\ the human shield of their believers' feelings.” —Richard | _o__) Stallman | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: datetime question
On Sat, 2009-10-31 at 20:34 +1100, Ben Finney wrote: Fixing ‘time’, ‘datetime’, and ‘calendar’ was the reason for Python 3? No, it wasn't. Or perhaps you mean that any backward-incompatible change was a reason to have Python 3? Even more firmly no. The extent of changes was severely limited to make the transition from Python 2 to Python 3 as painless as feasible, while still meeting the goals of Python 3. No, I meant cleaning up the standard library in spite of incompatibilities was one of the goals of Python3 (PEP 3108). Personally I don't see anything wrong with the modules, but that was my question to the person who said they should all be integrated but wasn't because of incompatibilities. -- http://mail.python.org/mailman/listinfo/python-list
Python 2.6.4: ./configure does not work
Hi, Running ./configure in the 2.6.4 sources produces the following error: config.status: error: cannot find input file: Makefile.pre.in Indeed, such a file is not contained anywhere in the Pakage. Also, I found this note: The Unix build and install process is explained clearly in the README file contained in the distribution (http://www.python.org/download/source/) However, there isn't any README (or INSTALL) file contained in the distribution. s...@mach:/home/sab/Python-2.6.4 find . -name README ./Lib/lib2to3/tests/data/README ./Lib/distutils/README ./Lib/test/crashers/README Any hints? Thanks, -Samuel -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
* sk: [title Why do you use python?] What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? (because my resume says I know C/C++/Java)? The C++ FAQ addresses this question here: url: http://www.parashift.com/c++-faq-lite/big-picture.html#faq-6.5 Cheers hth., - Alf -- http://mail.python.org/mailman/listinfo/python-list
Re. Web development with Python 3.1
Rober Kern wrote But if you insist, you may be interested in Breve: http://pypi.python.org/pypi/Breve/ Thanks for that! Viva internal DSLs! [Sorry -- cut my teeth on lisp] Is there anything like this for xml? Well I guess that is a slightly wrong (if not straight stupid) question. Maybe something along this line: Takes a spec as DTD or Relax-ng or somethn and produces something like Breve? -- http://mail.python.org/mailman/listinfo/python-list
Re: Working threads progress
Il Wed, 28 Oct 2009 20:04:45 -0700, ryles ha scritto: On Oct 28, 7:02 pm, mattia ger...@gmail.com wrote: Now, I would like to know the activity done (e.g. every two seconds) so I create another thread that checks the queue size (using .qsize()). Have you any suggestion to improve the code? It's not uncommon to pass each thread a second queue for output, which in your case might be tuples of (item, result). You can read from this queue in a single thread, and since the results now accumulate incrementally, you can easily collect more detailed status/progress information (if that's what you're looking for). OK, but what do you mean by 'read from this queue'? I mean, I can have a variable initialized when the working queue is full (e.g. ready to be used) and then every time i use queue.get() decrement the variable (using a lock in order to prevent concurrent access). Is what you had in mind? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python 2.6.4: ./configure does not work
On Sat, 2009-10-31 at 03:07 -0700, knipknap wrote: Hi, Running ./configure in the 2.6.4 sources produces the following error: config.status: error: cannot find input file: Makefile.pre.in Indeed, such a file is not contained anywhere in the Pakage. Which sources are you referring to? Can you verify the checksums: 17dcac33e4f3adb69a57c2607b6de246 13322131 Python-2.6.4.tgz fee5408634a54e721a93531aba37f8c1 11249486 Python-2.6.4.tar.bz2 Also, I found this note: The Unix build and install process is explained clearly in the README file contained in the distribution (http://www.python.org/download/source/) However, there isn't any README (or INSTALL) file contained in the distribution. s...@mach:/home/sab/Python-2.6.4 find . -name README ./Lib/lib2to3/tests/data/README ./Lib/distutils/README ./Lib/test/crashers/README Any hints? There is a README at the root of the tarball: $ pwd /home/marduk/Desktop/Python-2.6.4 $ head -1 README This is Python version 2.6.4 -- http://mail.python.org/mailman/listinfo/python-list
Re: Python 2.6.4: ./configure does not work
On 31 Okt., 11:40, Albert Hopkins mar...@letterboxes.org wrote: Which sources are you referring to? Can you verify the checksums: 17dcac33e4f3adb69a57c2607b6de246 13322131 Python-2.6.4.tgz fee5408634a54e721a93531aba37f8c1 11249486 Python-2.6.4.tar.bz2 There is a README at the root of the tarball: Huh, looks like the .bz2 package is broken (even though the md5 is fine). The .gz works fine. Thanks, -Samuel -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
sk a écrit : What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? As far as I'm concerned, I'd put it the other way round : where would I use C/C++/Java over Python ?-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
In message mailman.2365.1256979069.2807.python-l...@python.org, Albert Hopkins wrote: On Sat, 2009-10-31 at 21:32 +1300, Lawrence D'Oliveiro wrote: In message 6e603d9c-2be0-449c-9c3c-bab49e09e...@13g2000prl.googlegroups.com, Carl Banks wrote: Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? I think as someone pointed out earlier, in Unix-like operating systems, a regular library's file name starts with lib, e.g. libcrypt.so. So this would not conflict with Python's crypt.so. I just checked my Debian installation: l...@theon:~ find /lib /usr/lib -name \*.so -a -not -name lib\* -print | wc -l 2950 l...@theon:~ find /lib /usr/lib -name \*.so -print | wc -l 4708 So 63% of the shareable libraries on my system have names NOT beginning with lib. Any better theories? -- http://mail.python.org/mailman/listinfo/python-list
Re: Aaaargh! global name 'eggz' is not defined
On 10/29/09 9:48 PM, kj wrote: How can one check that a Python script is lexically correct? You can use a pseudo-static analyzer like pyflakes, pylint or pydoctor. Or, better, you can avoid wild imports, excessive local or global namespace manipulation, and break you program in smaller parts and write unit tests for them. Typos are very common but should very easy to catch. If you're not catching them until a very long run of your program, then your code coverage is probably too low. -- Alan Franzoni contact me at pub...@[mysurname].eu -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Oct 31, 1:32 am, Lawrence D'Oliveiro l...@geek- central.gen.new_zealand wrote: In message 6e603d9c-2be0-449c-9c3c- bab49e09e...@13g2000prl.googlegroups.com, Carl Banks wrote: It's not Python that's the issue. The issue is that if you have a module with a .dll extension, other programs could accidentally try to load that module instead of the intended dll, if the module is in the current directory or system path. Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? -- http://mail.python.org/mailman/listinfo/python-list
problem with read() write()
Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Oct 31, 1:32 am, Lawrence D'Oliveiro l...@geek- central.gen.new_zealand wrote: In message 6e603d9c-2be0-449c-9c3c- bab49e09e...@13g2000prl.googlegroups.com, Carl Banks wrote: It's not Python that's the issue. The issue is that if you have a module with a .dll extension, other programs could accidentally try to load that module instead of the intended dll, if the module is in the current directory or system path. Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? Unix doesn't search the executable path or current directory when loading libraries, which if you would have seen if you hadn't ignored my original reply. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
* Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Sat, 2009-10-31 at 23:58 +1300, Lawrence D'Oliveiro wrote: I just checked my Debian installation: l...@theon:~ find /lib /usr/lib -name \*.so -a -not -name lib\* -print | wc -l 2950 l...@theon:~ find /lib /usr/lib -name \*.so -print | wc -l 4708 So 63% of the shareable libraries on my system have names NOT beginning with lib. Any better theories? Those are likely not system (sharable) libraries (e.g. libcrypt). These are probably plugins loaded by a specific program, for example PAM modules, ImageMagick plugins, python modules, etc. so since they are not in your library path the do not stand getting accidentally loaded (e.g. when a binary is linked against libcrypt.so). These libraries are loaded directly by the program using their exact path name and dlopen(). The issue with windows they were saying is that Windows will load the library with that name if it is in your current directory. So if you happen to have a python library called CRYPT.DLL and you are in that directory and try to run a program that loads CRYPT.DLL then you will be loading the python module instead of the Windows one (I have no idea if Windows has a CRYPT.DLL). OTOH this doesn't happen in Linux because a) programs wanting the system's crypt library are looking for libcrypt.so and b) Linux doesn't look in your current directory (by default) for libraries. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
On Oct 31, 11:31 am, Alf P. Steinbach al...@start.no wrote: * sk: [title Why do you use python?] What would be your answer if this question is asked to you in an interview? a modified version might be: Where would you use python over C/C++/Java? (because my resume says I know C/C++/Java)? The C++ FAQ addresses this question here: url:http://www.parashift.com/c++-faq-lite/big-picture.html#faq-6.5 Cheers hth., - Alf Mphf Even I have some agreement that the choice of a language it's more a business-driven issue I REALLY don't like that the techie weenie shouldn't be heard. Talks a guy that programmed a GUI on Motif using C (plain old C) in 2003 and takes almost forever (one year and a half), instead of using any other graphical toolkit because we can't afford to expend time on learning new languages... I think time to development (usually related to mystical bugs well hidden in layers and layers of code) it's an important thing to take into account. -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
* Zeynel: On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. Just a thought: try w+ instead of r+. Because if you do print( open.__doc__ ) as I recall it said something about w truncating the file? Cheers hth., - Alf -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
On Oct 31, 9:55 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. Just a thought: try w+ instead of r+. Because if you do print( open.__doc__ ) as I recall it said something about w truncating the file? Cheers hth., - Alf No :) I still got the same thing. -- http://mail.python.org/mailman/listinfo/python-list
Re: datetime question
Thanks, Rami, that will work. V On Sat, Oct 31, 2009 at 4:54 AM, Albert Hopkins mar...@letterboxes.orgwrote: On Sat, 2009-10-31 at 20:34 +1100, Ben Finney wrote: Fixing ‘time’, ‘datetime’, and ‘calendar’ was the reason for Python 3? No, it wasn't. Or perhaps you mean that any backward-incompatible change was a reason to have Python 3? Even more firmly no. The extent of changes was severely limited to make the transition from Python 2 to Python 3 as painless as feasible, while still meeting the goals of Python 3. No, I meant cleaning up the standard library in spite of incompatibilities was one of the goals of Python3 (PEP 3108). Personally I don't see anything wrong with the modules, but that was my question to the person who said they should all be integrated but wasn't because of incompatibilities. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
* Zeynel: On Oct 31, 9:55 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. Just a thought: try w+ instead of r+. Because if you do print( open.__doc__ ) as I recall it said something about w truncating the file? Cheers hth., - Alf No :) I still got the same thing. Hm. Now I had to look in the docs because I thought I'd given bad advice. Doc of 'open' says: The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the file without truncation. So with 'w+' the only way to get garbage is if 'read' reads beyond the end of file, or 'open' doesn't conform to the documentation. Testing with Python 3.1.1 under Windows XP Pro: example f = open( zilly, w+ ) f.write( garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage ) 63 f.close() f = open( zilly, r ) f.read() 'garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage' f.close() f.open( zilly, r+ ) Traceback (most recent call last): File stdin, line 1, in module AttributeError: '_io.TextIOWrapper' object has no attribute 'open' open( zilly, r+ ) _io.TextIOWrapper name='zilly' encoding='cp1252' f = open( zilly, r+ ) f.write( hello ) 5 f.seek( 0 ) 0 f.read() 'hellogegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage' f.close() f = open( zilly, w+ ) f.write( hello ) 5 f.seek( 0 ) 0 f.read() 'hello' f.close() /example The w+ works here. Even if I made a typing mistake and apparently left the file open in the middle there. Cheers hth., - Alf -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
Zeynel wrote: On Oct 31, 9:55 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f =pen(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f =pen(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. Just a thought: try w+ instead of r+. Because if you do print( open.__doc__ ) as I recall it said something about w truncating the file? Cheers hth., - Alf No :) I still got the same thing. When you ran the program, the file already existed. So you're mixing the old content and the new. If you don't want that, then don't use r+. When testing, you should start with the system in a known state. Try initializing (with a text editor for example) that file before trying the program. And if it still gives you problems, show us the data in the file before running your code, your new code, and the results you get. One thing that'd be useful is to actually assign the results of the read() function to a variable and print it. DaveA -- http://mail.python.org/mailman/listinfo/python-list
Scheduling used in the multiprocessing.Pool.map() function
Hi all, I have been using the map() function in the multiprocessing module to parallelize my tasks on a dual core CPU. My tasks are embarrassingly parallel, shared nothing tasks. In one of my runs, I found that the this function interleaves execution of two processes over a single list. So far so good. But the problem is that the last remnant job is executed serially. I mean that it seems that the job scheduling is essentially static, and the last piece does not execute in parallel. Why can't there be a task-stealing scheduler in multiprocessing? Each of my individual function call in map takes over half hour (Each function call internally calls out to c++ code). This could be a very useful addition to multiprocessing's utility. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
import bug
I'm running into an ugly bug, which, IMHO, is really a bug in the design of Python's module import scheme. Consider the following directory structure: ham |-- __init__.py |-- re.py `-- spam.py ...with the following very simple files: % head ham/*.py == ham/__init__.py == == ham/re.py == == ham/spam.py == import inspect I.e. only ham/spam.py is not empty, and it contains the single line import inspect. If I now run the innocent-looking ham/spam.py, I get the following error: % python26 ham/spam.py Traceback (most recent call last): File ham/spam.py, line 1, in module import inspect File /usr/local/python-2.6.1/lib/python2.6/inspect.py, line 35, in module import string File /usr/local/python-2.6.1/lib/python2.6/string.py, line 122, in module class Template: File /usr/local/python-2.6.1/lib/python2.6/string.py, line 116, in __init__ 'delim' : _re.escape(cls.delimiter), AttributeError: 'module' object has no attribute 'escape' or, similarly, % python3 ham/spam.py Traceback (most recent call last): File ham/spam.py, line 1, in module import inspect File /usr/local/python-3.0/lib/python3.0/inspect.py, line 36, in module import string File /usr/local/python-3.0/lib/python3.0/string.py, line 104, in module class Template(metaclass=_TemplateMetaclass): File /usr/local/python-3.0/lib/python3.0/string.py, line 98, in __init__ 'delim' : _re.escape(cls.delimiter), AttributeError: 'module' object has no attribute 'escape' My sin appears to be having the (empty) file ham/re.py. So Python is confusing it with the re module of the standard library, and using it when the inspect module tries to import re. I've tried a lot of things to appease Python on this one, including a liberal sprinkling of from __future__ import absolute_import all over the place (except, of course, in inspect.py, which I don't control), but to no avail. I also pored over pp. 149-151 of Beazley's Python Essential Reference (4th ed.) on anything that would shed light on this problem, and again, nothing. I give up: what's the trick? (Of course, renaming ham/re.py is hardly the trick. It's rather Procrustes' Bed.) BTW, it is hard for me to imagine of an argument that could convince me that this is not a design bug, and a pretty ugly one at that. But, as they say, hope springs eternal: is there a PEP on the subject? (I know that there's a PEP on absolute_import, but since absolute_import appears to be absolutely ineffectual here, I figure I must look elsewhere for enlightenment.) TIA! kynn -- http://mail.python.org/mailman/listinfo/python-list
Re: problem with read() write()
On Oct 31, 10:40 am, Alf P. Steinbach al...@start.no wrote: Thanks! This works. But I need to close the file before read and open it again with r, otherwise I get the garbage again. Can you give me the link where you got this in documentation: The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the file without truncation. Only place i could find it was in this bug report: http://bugs.python.org/issue5061 * Zeynel: On Oct 31, 9:55 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: On Oct 31, 9:23 am, Alf P. Steinbach al...@start.no wrote: * Zeynel: Hello, I've been studying the official tutorial, so far it's been fun, but today I ran into a problem with the write(). So, I open the file pw and write hello and read: f = open(pw, r+) f.write(hello) f.read() But read() returns a bunch of what looks like meta code: ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e \xa5\x02\x0b \x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n (S'exec' What am I doing wrong? Thank you. After the 'write' the current position in the file is after the hello, so reading will read further content from there. The following works (disclaimer: I'm utter newbie in Python, and didn't consult the documentation, and it's the first time I've seen the Python 'open'): f = open(pw, r+) f.write( hello ) f.seek( 0 ) # Go back to start of file f.read() f.close() Cheers hth., - Alf Thanks, but it didn't work for me. I still get the meta file. Although I see that hello is there. Just a thought: try w+ instead of r+. Because if you do print( open.__doc__ ) as I recall it said something about w truncating the file? Cheers hth., - Alf No :) I still got the same thing. Hm. Now I had to look in the docs because I thought I'd given bad advice. Doc of 'open' says: The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the file without truncation. So with 'w+' the only way to get garbage is if 'read' reads beyond the end of file, or 'open' doesn't conform to the documentation. Testing with Python 3.1.1 under Windows XP Pro: example f = open( zilly, w+ ) f.write( garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage ) 63 f.close() f = open( zilly, r ) f.read() 'garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage' f.close() f.open( zilly, r+ ) Traceback (most recent call last): File stdin, line 1, in module AttributeError: '_io.TextIOWrapper' object has no attribute 'open' open( zilly, r+ ) _io.TextIOWrapper name='zilly' encoding='cp1252' f = open( zilly, r+ ) f.write( hello ) 5 f.seek( 0 ) 0 f.read() 'hellogegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage' f.close() f = open( zilly, w+ ) f.write( hello ) 5 f.seek( 0 ) 0 f.read() 'hello' f.close() /example The w+ works here. Even if I made a typing mistake and apparently left the file open in the middle there. Cheers hth., - Alf -- http://mail.python.org/mailman/listinfo/python-list
python os.path.exists failure
Hi all, My code is as follows: path = r'C:/Program Files/testfolder/2.3/test.txt' if os.path.lexists(path): print 'Path Exists' else: print 'No file found in path - %s' %path print Popen(path, stdout=PIPE, shell=True).stdout.read() The output comes as No file found in path - C:/Program Files/testfolder/2.3/test.txt but the test.txt file is opened. The issue, I guess, is that the double quotes inside is failing the check. But without the double quotes, Popen fails. One solution, I can think is to check without double quotes, and then using some code, put the double quotes back inside, but it looks quite kludgy. What is the usual solution to this? -- http://mail.python.org/mailman/listinfo/python-list
Re: import bug
On Oct 31, 3:12 pm, kj no.em...@please.post wrote: I'm running into an ugly bug, which, IMHO, is really a bug in the design of Python's module import scheme. Consider the following directory structure: ham |-- __init__.py |-- re.py `-- spam.py ...with the following very simple files: % head ham/*.py == ham/__init__.py == == ham/re.py == == ham/spam.py == import inspect I.e. only ham/spam.py is not empty, and it contains the single line import inspect. If I now run the innocent-looking ham/spam.py, I get the following error: % python26 ham/spam.py Traceback (most recent call last): File ham/spam.py, line 1, in module import inspect File /usr/local/python-2.6.1/lib/python2.6/inspect.py, line 35, in module import string File /usr/local/python-2.6.1/lib/python2.6/string.py, line 122, in module class Template: File /usr/local/python-2.6.1/lib/python2.6/string.py, line 116, in __init__ 'delim' : _re.escape(cls.delimiter), AttributeError: 'module' object has no attribute 'escape' or, similarly, % python3 ham/spam.py Traceback (most recent call last): File ham/spam.py, line 1, in module import inspect File /usr/local/python-3.0/lib/python3.0/inspect.py, line 36, in module import string File /usr/local/python-3.0/lib/python3.0/string.py, line 104, in module class Template(metaclass=_TemplateMetaclass): File /usr/local/python-3.0/lib/python3.0/string.py, line 98, in __init__ 'delim' : _re.escape(cls.delimiter), AttributeError: 'module' object has no attribute 'escape' My sin appears to be having the (empty) file ham/re.py. So Python is confusing it with the re module of the standard library, and using it when the inspect module tries to import re. I've tried a lot of things to appease Python on this one, including a liberal sprinkling of from __future__ import absolute_import all over the place (except, of course, in inspect.py, which I don't control), but to no avail. I also pored over pp. 149-151 of Beazley's Python Essential Reference (4th ed.) on anything that would shed light on this problem, and again, nothing. I give up: what's the trick? (Of course, renaming ham/re.py is hardly the trick. It's rather Procrustes' Bed.) BTW, it is hard for me to imagine of an argument that could convince me that this is not a design bug, and a pretty ugly one at that. But, as they say, hope springs eternal: is there a PEP on the subject? (I know that there's a PEP on absolute_import, but since absolute_import appears to be absolutely ineffectual here, I figure I must look elsewhere for enlightenment.) TIA! kynn You can shift the location of the current directory further down the search path. Assuming sys.path[0] is ''... Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41) [GCC 4.3.3] on linux2 Type help, copyright, credits or license for more information. import sys sys.path = sys.path[1:] + [''] import spam spam.__file__ 'spam.pyc' hth Jon. hth, Jon. -- http://mail.python.org/mailman/listinfo/python-list
Re: python os.path.exists failure
On Sat, Oct 31, 2009 at 11:26 AM, koranthala koranth...@gmail.com wrote: Hi all, My code is as follows: path = r'C:/Program Files/testfolder/2.3/test.txt' if os.path.lexists(path): print 'Path Exists' else: print 'No file found in path - %s' %path print Popen(path, stdout=PIPE, shell=True).stdout.read() The output comes as No file found in path - C:/Program Files/testfolder/2.3/test.txt but the test.txt file is opened. The issue, I guess, is that the double quotes inside is failing the check. But without the double quotes, Popen fails. One solution, I can think is to check without double quotes, and then using some code, put the double quotes back inside, but it looks quite kludgy. Just out of curiosity, does 'C:/Program FIles/' even work on the Windows command line? The usual procedure is to put the entire path in quotes. r'C:\Program Files\...'. What is the usual solution to this? -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: import bug
kj, 31.10.2009 16:12: My sin appears to be having the (empty) file ham/re.py. So Python is confusing it with the re module of the standard library, and using it when the inspect module tries to import re. 1) it's a bad idea to name your own modules after modules in the stdlib 2) this has been fixed in Py3 Stefan -- http://mail.python.org/mailman/listinfo/python-list
PIL Image.fromarray( ... , mode=1 )
Does anyone know how to save two-tone images represented as numpy arrays? I handle grayscale images by converting to PIL Image objects (mode=L) and then use the PIL save method, but I cannot make this work with mode=1. I have tried both boolean arrays and uint8 arrays (mod 2). In both cases I get an image which is predominantly black, with thin white stripes (possibly for every 8 pixels). If, instead, multiply my (mod 2) image by 255, and then convert with mode=L, I get the expected random-noise-looking image. Does anyone have any ideas? What do I do wrong? What is the right/best way to save/convert two-tone images? I have not managed to find proper documentation for the Image.fromarray() method; the docstring seems to be empty )-: TIA :-- Hans Georg -- http://mail.python.org/mailman/listinfo/python-list
How to import only one module in a package when the package __init__.py has already imports the modules?
I have the following files, which are in the directory 'test'. The parent directory of 'test' is in $PYTHONPATH. I have 'from A import A' and 'from B import B' in '__init__.py', because I want to use 'test.A' and 'test.B' to refer to classes A and B rather than 'test.A.A' and 'test.B.B'. $ll -g total 24 -rw-r--r-- 1 staff 32 2009-10-31 10:41:47 __init__.py -rw-r--r-- 1 staff 235 2009-10-31 10:45:24 __init__.pyc -rw-r--r-- 1 staff 550 2009-10-31 10:45:24 B.pyc -rw-r--r-- 1 staff 550 2009-10-31 10:45:24 A.pyc -rw-r--r-- 1 staff 54 2009-10-31 10:46:03 A.py -rw-r--r-- 1 staff 54 2009-10-31 10:46:14 B.py $cat __init__.py from A import A from B import B $cat A.py class A: def __init__(self): print '__init__ A' $cat B.py class B: def __init__(self): print '__init__ B' Then I have the following python files to call the modules. However, because I have 'import A from A' in '__init__.py', I can not call 'test.A.A()' anymore. Even I only have 'import test.A', both modules 'A' and 'B' are imported. So 'import test.A' is essentially the same as 'import test'. I'm wondering if there is a way to make the following two things hold. Thank you1 1. When I 'import test', I can refer to class A as 'test.A'. 2. When I 'import test.A', I can refer to class A as 'test.A.A' and class B shall not be imported. $cat fail.py import test.A test.A.A() $python fail.py Traceback (most recent call last): File fail.py, line 2, in module test.A.A() AttributeError: class A has no attribute 'A' $cat main.py import test test.A() test.B() $python main.py __init__ A __init__ B $cat fail2.py import test.A test.A() test.B() $python fail2.py __init__ A __init__ B -- http://mail.python.org/mailman/listinfo/python-list
Re: Sqlite3. Substitution of names in query.
Lawrence D'Oliveiro wrote: In message mailman.2357.1256964121.2807.python-l...@python.org, Dennis Lee Bieber wrote: This way regular string interpolation operations (or whatever Python 3.x has replaced it with) are safe to construct the SQL, leaving only user supplied (or program generated) data values to be passed via the DB-API parameter system -- so that they are properly escaped and rendered safe. Mixing the two is another recipe for confusion and mistakes. Mixing the two is necessary. According to the SQL standard, parameters can only take the place of literal values. Parameters can't take the place of identifiers or keywords that make up the structure of the query. So, you use string manipulation to build the structure of the query, and then you use parameter binding to fill values into the query. They are two different tools for two fundamentally different jobs. As long as you understand what you're doing, there should be no confusion. (And if you don't understand what you're doing, you shouldn't be doing it!) -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
Re: self.__dict__ tricks
On 2009-10-31, Steven D'Aprano st...@remove-this-cybersource.com.au wrote:
Idiomatic Python is to use CamelCase for classes.
Can you point me to a discussion on Idiomatic Python, CamelCase and
other matters?
... See PEP 8:
http://www.python.org/dev/peps/pep-0008/
Got it. Thanks.
invalid parameter shouldn't raise the same error as failing an
attribute look-up. That's misleading and confusing.
What error class or other approach do you recommend?
Unless you have a good reason for doing something different, do what
Python built-ins do:
int('123', parrot=16)
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: 'parrot' is an invalid keyword argument for this function
Understood. I kyped that method from from an open source library module
and have been using it ever since.
I also should point out that your trick will fail if you are using
__slots__.
??. Will research that. Elaborate if you wish.
__slots__ are an optimization for making objects smaller than normal if
you have many millions of them:
http://docs.python.org/reference/datamodel.html#slots
Thanks.
If the class grows - and I expect it will - I'd prefer to stick with
the keywords approach. That approach also allows me to use a
dictionary to initialize the object.
You can still do that with named parameters.
...
class Parrot:
... def __init__(self, name='Polly', colour='blue',
p = Parrot(Sparky, 'white', Cockatoo)
data = dict(colour='red', name='Fred', foo=1)
p = Parrot(**data) # raise an error with bad input
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: __init__() got an unexpected keyword argument 'foo'
... OK. That makes sense. You have made a believer of me.
I really appreciate all the time you have taken with this.
Many programmers I know stay away from 'lists' such as this, because
they are afraid to show their ignorance. Me, I'm fearless, and I have
learned a lot that I might not have otherwise.
take care
--
Tim
t...@johnsons-web.com
http://www.akwebsoft.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On 10/31/2009 12:03 AM Peng Yu said...
Suppose that I have the following directory and files. I want to get
the canonical path of a file, a directory or a symbolic link.
For example, for 'b' below, I want to get its canonical path as
'/private/tmp/abspath/b'.
So, why isn't realpath working for you? It looks like it is, and it
works that way here:
os.path.realpath('/home/emile/vmlinuz')
'/root/vmlinuz-2.4.7-10'
Emile
--
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Re: import bug
In 4aec591e$0$7629$9b4e6...@newsspool1.arcor-online.net Stefan Behnel stefan...@behnel.de writes: kj, 31.10.2009 16:12: My sin appears to be having the (empty) file ham/re.py. So Python is confusing it with the re module of the standard library, and using it when the inspect module tries to import re. 1) it's a bad idea to name your own modules after modules in the stdlib Obviously, since it leads to the headaches this thread illustrates. But there is nothing intrisically wrong with it. The fact that it is problematic in Python is a design bug, plain and simple. There's no rational basis for it, and represents an unreasonable demand on module writers, since contrary to the tight control on reserved Python keywords, there does not seem to be a similar control on the names of stdlib modules. What if, for example, in the future it was decided that my_favorite_module name would become part of the standard library? This alone would cause code to break. 2) this has been fixed in Py3 In my post I illustrated that the failure occurs both with Python 2.6 *and* Python 3.0. Did you have a particular version of Python 3 in mind? kynn -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Oct 31, 6:49 am, Albert Hopkins mar...@letterboxes.org wrote: OTOH this doesn't happen in Linux because a) programs wanting the system's crypt library are looking for libcrypt.so and b) Linux doesn't look in your current directory (by default) for libraries. One other thing is that linux binaries are usually linked against a versioned .so file, so a random command would refernce libc.so.6 rather than libc.so. I don't think that's necessarily the case for all Unix-like OSes, though. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On Sat, Oct 31, 2009 at 11:26 AM, Emile van Sebille em...@fenx.com wrote:
On 10/31/2009 12:03 AM Peng Yu said...
Suppose that I have the following directory and files. I want to get
the canonical path of a file, a directory or a symbolic link.
For example, for 'b' below, I want to get its canonical path as
'/private/tmp/abspath/b'.
So, why isn't realpath working for you? It looks like it is, and it works
that way here:
os.path.realpath('/home/emile/vmlinuz')
'/root/vmlinuz-2.4.7-10'
My definition of 'realpath' is different from the definition of
'os.path.realpath'. But I'm not short what term I should use to
describe. I use the following example to show what I want.
In my example in the original post,
'/tmp/abspath/b' is a symbolic link to '/tmp/abspath/a' and '/tmp' is
a symbolic link to '/private/tmp'.
Therefore, I want to get '/private/tmp/abspath/b', rather than
'/private/tmp/abspath/a', as the canonical path of 'b'.
If the argument is a symbolic link os.path.realpath will return the
actually target of the symbolic link. However, I want the path of the
symbolic link rather than the path of the target.
Hope this is clear.
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Re: import bug
On Sat, 2009-10-31 at 16:27 +, kj wrote: 2) this has been fixed in Py3 In my post I illustrated that the failure occurs both with Python 2.6 *and* Python 3.0. Did you have a particular version of Python 3 in mind? I was not able to reproduce with my python3: $ head ham/*.py == ham/__init__.py == == ham/re.py == == ham/spam.py == import inspect $ python3 ham/spam.py $ python3 --version Python 3.1.1 -- http://mail.python.org/mailman/listinfo/python-list
Re: self.__dict__ tricks
Hendrik van Rooyen wrote: On Friday, 30 October 2009 17:28:47 MRAB wrote: Wouldn't it be clearer if they were called dromedaryCase and BactrianCase? :-) Ogden Nash: The Camel has a single hump- The Dromedary, two; Or the other way around- I'm never sure. - Are You? If you make the first letter a capital: Dromedary starts with D, 1 bump, 1 hump. Bactrian starts with B, 2 bumps, 2 humps. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
Peng Yu pengyu...@gmail.com wrote: I'm wondering if there is a way to make the following two things hold. Thank you1 1. When I 'import test', I can refer to class A as 'test.A'. 2. When I 'import test.A', I can refer to class A as 'test.A.A' and class B shall not be imported. No. Either import adds the name 'test' to the current namespace. That name in each case references the same thing. Your simplest solution would be to give the sub-modules lowercase filenames, then you can do: import test test.A() or import test.a test.a.A() or even import test.a test.b.B() It would probably be best though just to be consistent as to how you reference the classes: define a public interface for your package and stick to it. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On 10/31/2009 10:11 AM Peng Yu said...
My definition of 'realpath' is different from the definition of
'os.path.realpath'. But I'm not short what term I should use to
describe. I use the following example to show what I want.
In my example in the original post,
'/tmp/abspath/b' is a symbolic link to '/tmp/abspath/a' and '/tmp' is
a symbolic link to '/private/tmp'.
Therefore, I want to get '/private/tmp/abspath/b', rather than
'/private/tmp/abspath/a', as the canonical path of 'b'.
It still looks like it works here. I've set up a similar structure and
appear to get the results you're asking for using os.path.realpath.
# pwd
/home/emile
# ls -l
drwxr-xr-x 3 root root 4096 2009-10-31 10:25 private
lrwxrwxrwx 1 root root 11 2009-10-31 10:25 tmp - private/tmp
# pwd
/home/emile/tmp/abspath
# ls -l
-rw-r--r-- 1 root root 10 2009-10-31 10:25 a
lrwxrwxrwx 1 root root 1 2009-10-31 10:26 b - a
Python 2.6.3 (r263:75183, Oct 15 2009, 15:03:49) [GCC 4.3.2] on linux2
import os
os.path.realpath('/home/emile/tmp/a')
'/home/emile/private/tmp/a'
os.path.realpath('/home/emile/tmp/b')
'/home/emile/private/tmp/b'
If the argument is a symbolic link os.path.realpath will return the
actually target of the symbolic link.
However, I want the path of the
symbolic link rather than the path of the target.
Which is what I got above.
Hope this is clear.
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Re: list comprehension problem
alex23 wrote: Terry Reedy tjre...@udel.edu wrote: alex23 wrote: You're completely wrong. Immutability has nothing to do with identity, ... I'm honestly not getting your point here. Let me try again, a bit differently. I claim that the second statement, and therefor the first, can be seen as wrong. I also claim that (Python) programmers need to understand why. In mathematics, we generally have immutable values whose 'identity' is their value. There is, for example, only one, immutable, empty set. In informatics, and in particular in Python, in order to have mutability, we have objects with value and an identity that is separate from their value. There can be, for example, multiple mutable empty sets. Identity is important because we must care about which empty set we add things to. 'Identity' is only needed because of 'mutability', so it is mistaken to say they have nothing to do with each other. Ideally, from both a conceptual and space efficiency view, an implementation would allow only one copy for each value of immutable classes. This is what new programmers assume when they blithely use 'is' instead of '==' (as would usually be correct in math). However, for time efficiency reasons, there is no unique copy guarantee, so one must use '==' instead of 'is', except in those few cases where there is a unique copy guarantee, either by the language spec or by one's own design, when one must use 'is' and not '=='. Here 'must' means 'must to be generally assured of program correctness as intended'. We obviously agree on this guideline. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
Peng Yu wrote:
On Sat, Oct 31, 2009 at 11:26 AM, Emile van Sebille em...@fenx.com wrote:
On 10/31/2009 12:03 AM Peng Yu said...
Suppose that I have the following directory and files. I want to get
the canonical path of a file, a directory or a symbolic link.
For example, for 'b' below, I want to get its canonical path as
'/private/tmp/abspath/b'.
So, why isn't realpath working for you? It looks like it is, and it works
that way here:
os.path.realpath('/home/emile/vmlinuz')
'/root/vmlinuz-2.4.7-10'
My definition of 'realpath' is different from the definition of
'os.path.realpath'. But I'm not short what term I should use to
describe. I use the following example to show what I want.
In my example in the original post,
'/tmp/abspath/b' is a symbolic link to '/tmp/abspath/a' and '/tmp' is
a symbolic link to '/private/tmp'.
Therefore, I want to get '/private/tmp/abspath/b', rather than
'/private/tmp/abspath/a', as the canonical path of 'b'.
If the argument is a symbolic link os.path.realpath will return the
actually target of the symbolic link. However, I want the path of the
symbolic link rather than the path of the target.
Hope this is clear.
I suspect that you will have to write your own code for your own
function. os and os.path are written in Python, so look at the code for
realpath and modify it for your modified definition.
Terry Jan Reedy
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Re: problem with read() write()
Zeynel wrote: On Oct 31, 10:40 am, Alf P. Steinbach al...@start.no wrote: Thanks! This works. But I need to close the file before read and open it again with r, otherwise I get the garbage again. Can you give me the link where you got this in documentation: The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the file without truncation. Only place i could find it was in this bug report: http://bugs.python.org/issue5061 LibRef / builtin functions /open The entry is a full page. Get familiar with this section and the Built-in Types section. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: OT: DARPA red balloon challenge
Adam N wrote: All, In case people hadn't heard, DARPA just announced what I think is the coolest competition ever: http://networkchallenge.darpa.mil/ On December 5, DARPA will raise 10 red weather balloons somewhere in the US. The first person to get the location of all 10 balloons and submit them will be given $40k. You're thinking of doing this with people running around? Nah. The right way is to get some successive images of the earth from Digital Globe. They just launched their WorldView-2 satellite. http://www.satimagingcorp.com/satellite-sensors/worldview-2.html They image the whole planet at 0.42m resolution in color every two days. Upload that to some cloud system and find all red dots in the continental US that weren't there before the event. John Nagle -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On Sat, Oct 31, 2009 at 1:10 PM, Emile van Sebille em...@fenx.com wrote:
On 10/31/2009 10:11 AM Peng Yu said...
My definition of 'realpath' is different from the definition of
'os.path.realpath'. But I'm not short what term I should use to
describe. I use the following example to show what I want.
In my example in the original post,
'/tmp/abspath/b' is a symbolic link to '/tmp/abspath/a' and '/tmp' is
a symbolic link to '/private/tmp'.
Therefore, I want to get '/private/tmp/abspath/b', rather than
'/private/tmp/abspath/a', as the canonical path of 'b'.
It still looks like it works here. I've set up a similar structure and
appear to get the results you're asking for using os.path.realpath.
# pwd
/home/emile
# ls -l
drwxr-xr-x 3 root root 4096 2009-10-31 10:25 private
lrwxrwxrwx 1 root root 11 2009-10-31 10:25 tmp - private/tmp
# pwd
/home/emile/tmp/abspath
# ls -l
-rw-r--r-- 1 root root 10 2009-10-31 10:25 a
lrwxrwxrwx 1 root root 1 2009-10-31 10:26 b - a
Python 2.6.3 (r263:75183, Oct 15 2009, 15:03:49) [GCC 4.3.2] on linux2
import os
os.path.realpath('/home/emile/tmp/a')
'/home/emile/private/tmp/a'
os.path.realpath('/home/emile/tmp/b')
'/home/emile/private/tmp/b'
If the argument is a symbolic link os.path.realpath will return the
actually target of the symbolic link. However, I want the path of the
symbolic link rather than the path of the target.
Which is what I got above.
I'm curious why we get different results. I tried on both linux and
mac. Both of them give me the same results.
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Re: Python newbie data structures question
On Oct 29, 2:06 am, Chris Rebert c...@rebertia.com wrote:
On Wed, Oct 28, 2009 at 11:31 PM, codingJoe tracy.monte...@gmail.com wrote:
Hi all!
I am trying to choose the right data structure to do a value lookup
with multiple keys.
I want to lookup data by: key, key,{ values }
My final product should be able to reference this datastructure from
within a django template.
Because my lookup needs only 80 values and will never change, it seems
that I could just build some type of data structure or object. My
rudamentary approach is to do lots of looping, but there must be a
better way to do this.
A dictionary object only has (key, value). The same pair of keys
could return multiple values.
Tuples might work, but I just don't understand them enough.
the simple exampe is a quick lookup index the available sport by
season that returns one or many value. The values would be data
structures and contain more than just the name, but also things like
uniform color, team size.
indoors outdoors
---
winter | bball | skiing |
| | sledding |
|--
| | baseball |
summer| raquetball | soccer |
| | |
|
|--
Advice? What data structure should I use? And a simple newbie
example please..
Besides Alex's option of using tuples as dictionary keys:
A. An SQL database
(http://docs.python.org/library/sqlite3.html#module-sqlite3). Overkill
for something as simple as your toy example, but in analogous but more
complicated cases, it's one method to consider.
B. Nested dictionaries. Particularly useful if you want to access the
data by broader categories (e.g. all summer sports), although it only
works for one axis of categories (i.e. season or doors-ness); if you
want to access by the other axis, you have to code it yourself.
Example:
sports = {winter : {indoors:[bball], outdoors:[skiing,
sledding]}, summer : {indoors:[raquetball],
outdoors:[baseball,soccer]} }
bball = sports[winter][indoors][0]
baseball, soccer = sports[summer][outdoors]
all_summer_sports = sum(sports[summer].values(), [])
Cheers,
Chris
--http://blog.rebertia.com- Hide quoted text -
- Show quoted text -
Nice, both examples work well on the Python side. Now I am trying to
print the values from a Django template. I've nested them in a table
similar to the example above to be rendered in a web page. How do I
do that?
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Re: problem with read() write()
On Oct 31, 3:11 pm, Terry Reedy tjre...@udel.edu wrote: Great, thanks. Zeynel wrote: On Oct 31, 10:40 am, Alf P. Steinbach al...@start.no wrote: Thanks! This works. But I need to close the file before read and open it again with r, otherwise I get the garbage again. Can you give me the link where you got this in documentation: The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the file without truncation. Only place i could find it was in this bug report:http://bugs.python.org/issue5061 LibRef / builtin functions /open The entry is a full page. Get familiar with this section and the Built-in Types section. Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On Sat, Oct 31, 2009 at 1:46 PM, Terry Reedy tjre...@udel.edu wrote:
Peng Yu wrote:
On Sat, Oct 31, 2009 at 11:26 AM, Emile van Sebille em...@fenx.com
wrote:
On 10/31/2009 12:03 AM Peng Yu said...
Suppose that I have the following directory and files. I want to get
the canonical path of a file, a directory or a symbolic link.
For example, for 'b' below, I want to get its canonical path as
'/private/tmp/abspath/b'.
So, why isn't realpath working for you? It looks like it is, and it
works
that way here:
os.path.realpath('/home/emile/vmlinuz')
'/root/vmlinuz-2.4.7-10'
My definition of 'realpath' is different from the definition of
'os.path.realpath'. But I'm not short what term I should use to
describe. I use the following example to show what I want.
In my example in the original post,
'/tmp/abspath/b' is a symbolic link to '/tmp/abspath/a' and '/tmp' is
a symbolic link to '/private/tmp'.
Therefore, I want to get '/private/tmp/abspath/b', rather than
'/private/tmp/abspath/a', as the canonical path of 'b'.
If the argument is a symbolic link os.path.realpath will return the
actually target of the symbolic link. However, I want the path of the
symbolic link rather than the path of the target.
Hope this is clear.
I suspect that you will have to write your own code for your own function.
os and os.path are written in Python, so look at the code for realpath and
modify it for your modified definition.
I find the following two files that define realpath. But I don't find
'realpath' in os.py. I looked at 'os.py'. But I don't understand how
the function realpath is introduced in the name space in os.path.
Would you please let me know?
gfind . ! -path '*backup*' -name *.py -type f -exec grep -n def
realpath {} \; -printf %p\\n\\n
193:def realpath(path):
./macpath.py
345:def realpath(filename):
./posixpath.py
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Re: Python 2.6.4: ./configure does not work
In article bdb4ce25-22ea-4e83-8e73-ae53cd125...@a31g2000yqn.googlegroups.com, knipknap knipk...@gmail.com wrote: Huh, looks like the .bz2 package is broken (even though the md5 is fine). The .gz works fine. Hmm, the .bz2 from the official download page http://www.python.org/download/releases/2.6.4/ seems to have a perfectly good README and Makefile.pre.in. Problem with your version of tar or ... ? -- Ned Deily, n...@acm.org -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 12:47 PM, Duncan Booth duncan.bo...@invalid.invalid wrote: Peng Yu pengyu...@gmail.com wrote: I'm wondering if there is a way to make the following two things hold. Thank you1 1. When I 'import test', I can refer to class A as 'test.A'. 2. When I 'import test.A', I can refer to class A as 'test.A.A' and class B shall not be imported. No. Either import adds the name 'test' to the current namespace. That name in each case references the same thing. Your simplest solution would be to give the sub-modules lowercase filenames, then you can do: import test test.A() or import test.a test.a.A() or even import test.a test.b.B() It would probably be best though just to be consistent as to how you reference the classes: define a public interface for your package and stick to it. The original problem comes from the maintenance of the package. When A and B are large classes, it is better to put them in separate files under the directory 'test' than put them in the file 'test.py'. The interface 'test.A' is used by end users. However, there will be a problem if 'import test' is used for developers, because both A and B are imported, which cause dependence between A and B. For example, during the modification of B (not finished), 'import A' would not work. This is means that modifications of A and B are not independent, which cause a lot of problem when maintaining the package. Naming the filename different from the class is a solution, but it is a little bit annoying. I'm wondering how people handle this situation when they have to separate a module into multiple modules. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On 2009-10-31 15:31 PM, Peng Yu wrote: The original problem comes from the maintenance of the package. When A and B are large classes, it is better to put them in separate files under the directory 'test' than put them in the file 'test.py'. The interface 'test.A' is used by end users. However, there will be a problem if 'import test' is used for developers, because both A and B are imported, which cause dependence between A and B. For example, during the modification of B (not finished), 'import A' would not work. This is means that modifications of A and B are not independent, which cause a lot of problem when maintaining the package. To be frank, that development process is going to cause you a lot of problems well beyond these import entanglements. Developers should have their own workspace! They shouldn't push things into production until the system is working. Checking something into source control shouldn't automatically deploy things into production. Naming the filename different from the class is a solution, but it is a little bit annoying. I'm wondering how people handle this situation when they have to separate a module into multiple modules. Even if we organize things along the lines of one class per module, we use different capitalization conventions for modules and classes. In part, this helps solve your problem, but it mostly saves the developer thought-cycles from having to figure out which you are referring to when reading the code. Personally, I like to keep my __init__.py files empty such that I can import exactly what I need from the package. This allows me to import exactly the module that I need. In large packages with extension modules that can be expensive to load, this is useful. We usually augment this with an api.py that exposes the convenient public API of the package, the A and B classes in your case. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 4:14 PM, Robert Kern robert.k...@gmail.com wrote: On 2009-10-31 15:31 PM, Peng Yu wrote: The original problem comes from the maintenance of the package. When A and B are large classes, it is better to put them in separate files under the directory 'test' than put them in the file 'test.py'. The interface 'test.A' is used by end users. However, there will be a problem if 'import test' is used for developers, because both A and B are imported, which cause dependence between A and B. For example, during the modification of B (not finished), 'import A' would not work. This is means that modifications of A and B are not independent, which cause a lot of problem when maintaining the package. To be frank, that development process is going to cause you a lot of problems well beyond these import entanglements. Developers should have their own workspace! They shouldn't push things into production until the system is working. Checking something into source control shouldn't automatically deploy things into production. I don't quite agree with your opinion. But please don't take it too personaly. Even in the developer's work space, it is possible to change multiple classes simultaneously. So the import entanglement problem still exists. Naming the filename different from the class is a solution, but it is a little bit annoying. I'm wondering how people handle this situation when they have to separate a module into multiple modules. Even if we organize things along the lines of one class per module, we use different capitalization conventions for modules and classes. In part, this helps solve your problem, but it mostly saves the developer thought-cycles from having to figure out which you are referring to when reading the code. I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). When one class per module is strictly enforced, there will be no need to have different capitalization conventions for modules and classes. Developers should be able to tell whether it is a class or a module from the context. In my question, module A and B exist just for the sake of implementation. Even if I have module A and B, I don't want the user feel the existence of module A and B. I want them feel exact like class A and B are defined in module 'test' instead of feeling two modules A and B are in package 'test'. I know that module names should be in lower cases, in general. However, it is OK to have the module name capitalized in this case since the end users don't see them. In C++, what I am asking can be easily implemented, because the namespace and the directory hierachy is not bind to each other. However, the binding between the namespace and the directory hierachy make this difficult to implement. I don't know if it is not impossible, but I'd hope there is a way to do so. Personally, I like to keep my __init__.py files empty such that I can import exactly what I need from the package. This allows me to import exactly the module that I need. In large packages with extension modules that can be expensive to load, this is useful. We usually augment this with an api.py that exposes the convenient public API of the package, the A and B classes in your case. I looked at python library, there are quite a few __init__.py files are not empty. In fact, they are quite long. I agree with you that '__init__.py' should not be long. But I'm wondering why in python library __init__.py are quite long. -- http://mail.python.org/mailman/listinfo/python-list
Re: datetime question
Albert Hopkins mar...@letterboxes.org writes: No, I meant cleaning up the standard library in spite of incompatibilities was one of the goals of Python3 (PEP 3108). Ah, okay. That PEP is “Standard Library Reorganization” URL:http://www.python.org/dev/peps/pep-3108/, and is specifically about removing or renaming modules to “clean up” the library. I don't think it applies to this conversation, which is not about renaming nor removing modules. Personally I don't see anything wrong with the modules, but that was my question to the person who said they should all be integrated but wasn't because of incompatibilities. The changes I'm suggesting would be necessary are to the behaviour of the ‘time’, ‘datetime’, and ‘calendar’ modules: the types they consume and produce would be unified. They're not now, which would represent an incompatible API change, not covered by PEP 3108 nor any Python 2→3 PEP to my knowledge. -- \ “Alternative explanations are always welcome in science, if | `\ they are better and explain more. Alternative explanations that | _o__) explain nothing are not welcome.” —Victor J. Stenger, 2001-11-05 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Why do you use python?
For me a language is a language for the most part, doesn't matter... Python is a language I choose for any of several reasons: 0.) It is easy to setup dependent packages on both BSD, Linux, and Windows 1.) Most important things already have a Python binding somewhere 2.) Working in Python is fun 3.) Python scripts are more portable between OSes then compiled executables. I find that Python makes me very productive, and lets me worry more about the engineering side of the art. However, I'm just as happy using C or a portable subset of sh. Unless it means writing Swing layouts by hand. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the realpath of a symbolic link?
On Sat, Oct 31, 2009 at 14:48 -0500, Peng Yu wrote:
On Sat, Oct 31, 2009 at 1:46 PM, Terry Reedy tjre...@udel.edu wrote:
Peng Yu wrote:
[ snip ]
I find the following two files that define realpath. But I don't find
'realpath' in os.py. I looked at 'os.py'. But I don't understand how
the function realpath is introduced in the name space in os.path.
Would you please let me know?
gfind . ! -path '*backup*' -name *.py -type f -exec grep -n def
realpath {} \; -printf %p\\n\\n
193:def realpath(path):
./macpath.py
345:def realpath(filename):
./posixpath.py
The os module needs to support different platforms. The os.path module
is actually one of the platform specific ones (ntpath, posixpath,
...) that are imported 'as path' depending on the platform the code is
executed.
Have a look at the source code of the os module:
--- os.py - Python 2.6.3 ---
...
f 'posix' in _names:
...
import posixpath as path
elif 'nt' in _names:
...
import ntpath as path
import nt
__all__.extend(_get_exports_list(nt))
del nt
...
else:
raise ImportError, 'no os specific module found'
sys.modules['os.path'] = path
--- snip ---
If you really want to understand how a module is working then have a
look at its source code. Python is open source -- Use that privilige!
kind regards
Wolodja Wentland
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Description: Digital signature
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Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 4:14 PM, Robert Kern robert.k...@gmail.com wrote: [ snip ] I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. regards Wolodja signature.asc Description: Digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On 2009-10-31 16:53 PM, Peng Yu wrote: On Sat, Oct 31, 2009 at 4:14 PM, Robert Kernrobert.k...@gmail.com wrote: On 2009-10-31 15:31 PM, Peng Yu wrote: The original problem comes from the maintenance of the package. When A and B are large classes, it is better to put them in separate files under the directory 'test' than put them in the file 'test.py'. The interface 'test.A' is used by end users. However, there will be a problem if 'import test' is used for developers, because both A and B are imported, which cause dependence between A and B. For example, during the modification of B (not finished), 'import A' would not work. This is means that modifications of A and B are not independent, which cause a lot of problem when maintaining the package. To be frank, that development process is going to cause you a lot of problems well beyond these import entanglements. Developers should have their own workspace! They shouldn't push things into production until the system is working. Checking something into source control shouldn't automatically deploy things into production. I don't quite agree with your opinion. But please don't take it too personaly. Even in the developer's work space, it is possible to change multiple classes simultaneously. So the import entanglement problem still exists. But it's a problem that should have different consequences than you are claiming. Having users prevented from using A because developers are modifying their copy of B in production is a problem that needs to be solved by changing your development process. If you don't change your development process, you will run into the same problems without import entanglements. Now as to import entanglements in the developer's workspace, it is true that they can cause issues from time to time, but they are much, much smaller in practice. I can just go in and comment out the offending import temporarily while I finish working on the other part until I'm ready to address both of them together. Then when I'm finished and things are working again, I can check my code into source control. It's just not a big deal. Naming the filename different from the class is a solution, but it is a little bit annoying. I'm wondering how people handle this situation when they have to separate a module into multiple modules. Even if we organize things along the lines of one class per module, we use different capitalization conventions for modules and classes. In part, this helps solve your problem, but it mostly saves the developer thought-cycles from having to figure out which you are referring to when reading the code. I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). One function per file is a little extreme. I am sympathetic to one class per module, but functions *should* be too short too warrant a module to themselves. When one class per module is strictly enforced, there will be no need to have different capitalization conventions for modules and classes. Developers should be able to tell whether it is a class or a module from the context. Given enough brain-time, but you can make your code easier to read by using different conventions for different things. Developer brain-time is expensive! As much as possible, it should be spent on solving problems, not comprehension. In my question, module A and B exist just for the sake of implementation. Even if I have module A and B, I don't want the user feel the existence of module A and B. I want them feel exact like class A and B are defined in module 'test' instead of feeling two modules A and B are in package 'test'. I know that module names should be in lower cases, in general. However, it is OK to have the module name capitalized in this case since the end users don't see them. In C++, what I am asking can be easily implemented, because the namespace and the directory hierachy is not bind to each other. However, the binding between the namespace and the directory hierachy make this difficult to implement. I don't know if it is not impossible, but I'd hope there is a way to do so. I'm not sure that C++ is a lot better. I still have to know the file hierarchy in order to #include the right files. Yes, the namespaces get merged when you go to reference things in the code, but those #includes are intimately tied to the file hierarchy. In C++, you can often #include one file that #includes everything else because linking won't bring in the symbols you don't actually use. Oddly enough, we don't have that luxury because we are in a dynamic language. Python imports have runtime consequences because there is no compile or link step. You can't think of import statements as #include statements and need to use different patterns. Of course, to really take advantage of that
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 5:45 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 4:14 PM, Robert Kern robert.k...@gmail.com wrote: [ snip ] I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. If two functions are too long to put in file, I generally put them in two different files. And I always put a single class in a file. Suppose that I have many functions in one file, it is not clear to see how many functions are in the file at first glance. If I put each function in its own file, just by looking at the directory structure, I can easily see how many functions there are. One advantage is on refactoring. When each function has its own file, I can change variable names, etc., for a give function without worrying accidentally change variable names in other functions. When I find a function is more appropriate to put in another namespace, I can just move the file around. Another advantage is on testing. I can have associated test dir for each class or function. By this way I can easily locate the definition and the test to track any potential problems. You can use package rather than module to group semantic related classes and functions. -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) iQIcBAEBCAAGBQJK7L38AAoJEIt/fTDK8U78Pv4P/icEwsmSLcuINWZHj4Shs0A/ 1/TZcuP5VwuR6gZ0WsywKzbKJqL0WDahUi4o3VkwFuM2mKskXzch3buZ5NvlwOp6 I+NqBn9jCTb3nXiVb5wHdF6uYf84BPZe1WccRIDJLIoGRWX/V6tmMH1LtLGnBeVi RGOd6Mz2KGr1cgisyYJ2h4Qm5tzKNuZ1KDtzXoOG4DYzwEEZBITFOwDNXy5tihJz v/NcAZOa4aBfJZtKxA7Ikl+30nDV8ZZhEU7Br/rIus2JrSqMp6gAh4f+zTz9jQzL Sp7O3bTQiHoghej+G4YW+/eMDTiNDSKm1u8++V5svwednp/mmYBnzA8aIPKFSoN6 vn4D0Q2XVGQAoWyY7pT9zyRKBJnn63xXD5h9T6JimEz7uMWGzTebIuxFRHsd1vkt TYTW1kJDH8aIsy51egBezZx8o6sntBFu3D+D3itqDW2D2sZ75sPiblgkLCWHvZMR RaBjCkvhVjOaiJOZ64mRmkW3RUJzY6lGvEqfQqW1bRpHxLEUKaWLy6rWa0sQTTut rIZ/5TdnjPec1Dx+9v6V7sW8bZtCttpb7j4k+DBAMjRpW7mocnGfuxGN/57Y/uD0 gFOURpMz1rjEdPCiYZuUQX+joS3tl9IxnBZL7gTRl3slSWoVlGuhcqsew3nAkrGB Fx8iwKUAwwRULxzigHHB =n3s3 -END PGP SIGNATURE- -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Why 'import module' will not import module.py but the directory module?
If I have both the directory 'module' and the file 'module.py' in a directory in $PYTHONPATH, python will import 'module' rather than 'module.py'. I'm wondering what is the design rationale of setting higher priorities to directories. Is there a way to reverse the priority? -- http://mail.python.org/mailman/listinfo/python-list
Re: Sqlite3. Substitution of names in query.
In message mailman.2376.1257005738.2807.python-l...@python.org, Carsten Haese wrote: Lawrence D'Oliveiro wrote: In message mailman.2357.1256964121.2807.python-l...@python.org, Dennis Lee Bieber wrote: This way regular string interpolation operations (or whatever Python 3.x has replaced it with) are safe to construct the SQL, leaving only user supplied (or program generated) data values to be passed via the DB-API parameter system -- so that they are properly escaped and rendered safe. Mixing the two is another recipe for confusion and mistakes. Mixing the two is necessary. ... As long as you understand what you're doing, there should be no confusion. (And if you don't understand what you're doing, you shouldn't be doing it!) But if you understand what you're doing, you don't need to mix the two. -- http://mail.python.org/mailman/listinfo/python-list
Re: Why 'import module' will not import module.py but the directory module?
On 2009-10-31 18:51 PM, Peng Yu wrote: If I have both the directory 'module' and the file 'module.py' in a directory in $PYTHONPATH, python will import 'module' rather than 'module.py'. I'm wondering what is the design rationale of setting higher priorities to directories. Is there a way to reverse the priority? You mean that you have a package module/? With an __init__.py? Plain directories that aren't packages shouldn't be imported by Python. No, you can't reverse the priority between packages and modules. I'm not sure why that would help you. The package would then be inaccessible if you did. If it's inaccessible, then why have it at all? -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Sqlite3. Substitution of names in query.
Lawrence D'Oliveiro wrote: In message mailman.2376.1257005738.2807.python-l...@python.org, Carsten Haese wrote: Lawrence D'Oliveiro wrote: In message mailman.2357.1256964121.2807.python-l...@python.org, Dennis Lee Bieber wrote: This way regular string interpolation operations (or whatever Python 3.x has replaced it with) are safe to construct the SQL, leaving only user supplied (or program generated) data values to be passed via the DB-API parameter system -- so that they are properly escaped and rendered safe. Mixing the two is another recipe for confusion and mistakes. Mixing the two is necessary. ... As long as you understand what you're doing, there should be no confusion. (And if you don't understand what you're doing, you shouldn't be doing it!) But if you understand what you're doing, you don't need to mix the two. Are we talking about the same thing here? I thought we're talking about string interpolation and parameter binding, and I explained that mixing those two is necessary if you have a query in which the movable bits are identifiers or other syntax elements. On what grounds are you asserting that it's not necessary to mix the two? Please elaborate your point. -- Carsten Haese http://informixdb.sourceforge.net -- http://mail.python.org/mailman/listinfo/python-list
Re: Why 'import module' will not import module.py but the directory module?
On Sat, Oct 31, 2009 at 7:02 PM, Robert Kern robert.k...@gmail.com wrote: On 2009-10-31 18:51 PM, Peng Yu wrote: If I have both the directory 'module' and the file 'module.py' in a directory in $PYTHONPATH, python will import 'module' rather than 'module.py'. I'm wondering what is the design rationale of setting higher priorities to directories. Is there a way to reverse the priority? You mean that you have a package module/? With an __init__.py? Plain directories that aren't packages shouldn't be imported by Python. Yes. I mean a pakcage 'module/' with an __init__.py. No, you can't reverse the priority between packages and modules. I'm not sure why that would help you. The package would then be inaccessible if you did. If it's inaccessible, then why have it at all? Why the package 'module' has to be inaccessible? I can 'import module.part1' to access the component of the package. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 18:29 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 5:45 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. If two functions are too long to put in file, I generally put them in two different files. If it should ever happen that two functions are too long to put in a single file you should refactor your code. It is usually a good idea of breaking problems down into single steps (ie functions) so you never end up with a 5000 SLOC *function*. How do functions of this length enhance the readability of your source code? And I always put a single class in a file. Why? What do you gain by that? Suppose that I have many functions in one file, it is not clear to see how many functions are in the file at first glance. Use a better editor/IDE for that. [snip] I thought about answering your post in greater detail, but i would like to evaluate your style of work first. Is there any place where I can have a look at some of your source code? It would be perfect if it is a medium sized project with said unit tests, packages and function-modules and the rest you described. Why does not a single module in in the stdlib follow your code layout scheme? regards Wolodja signature.asc Description: Digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Why 'import module' will not import module.py but the directory module?
On 2009-10-31 19:16 PM, Peng Yu wrote: On Sat, Oct 31, 2009 at 7:02 PM, Robert Kernrobert.k...@gmail.com wrote: On 2009-10-31 18:51 PM, Peng Yu wrote: If I have both the directory 'module' and the file 'module.py' in a directory in $PYTHONPATH, python will import 'module' rather than 'module.py'. I'm wondering what is the design rationale of setting higher priorities to directories. Is there a way to reverse the priority? You mean that you have a package module/? With an __init__.py? Plain directories that aren't packages shouldn't be imported by Python. Yes. I mean a pakcage 'module/' with an __init__.py. No, you can't reverse the priority between packages and modules. I'm not sure why that would help you. The package would then be inaccessible if you did. If it's inaccessible, then why have it at all? Why the package 'module' has to be inaccessible? I can 'import module.part1' to access the component of the package. No, it wouldn't. It's a moot point because Python picks the package first, but if it did pick modules before packages, then sys.modules['module'] would point to the module from module.py and not module/__init__.py . import module.part1 first executes import module, then looks in there to determine who to resolve module.part1. Since sys.modules['module'] is a regular module and not the package, it wouldn't find module/part1.py . -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Problems in merge.py when building the Python MSI installer
I'm trying to build a Python MSI installer for Windows using the scripts provided at Tools\msi\ msi.py runs fine and generates a python-xxx.msi file. Then, when I run the merge.py script, I get these error messages: e:\prog\python\py3k\Tools\msi\msilib.py:8: DeprecationWarning: the sets module i s deprecated import re, string, os, sets, glob, subprocess, sys, _winreg, struct Opened Log Opened DB C:\Archivos de programa\Archivos comunes\Merge Modules\Microsoft_VC90_CRT_x86.ms m Opened Module C:\Archivos de programa\Archivos comunes\Merge Modules\Microsoft_V C90_CRT_x86.msm Errors: 4 _Validation _Validation Modkeys: _Validation Nullable DBKeys: _Validation Nullable 4 _Validation _Validation Modkeys: CustomAction Type DBKeys: CustomAction Type 4 _Validation _Validation Modkeys: File Sequence DBKeys: File Sequence C:\Archivos de programa\Archivos comunes\Merge Modules\policy_9_0_Microsoft_VC90 _CRT_x86.msm Opened Module C:\Archivos de programa\Archivos comunes\Merge Modules\policy_9_0_ Microsoft_VC90_CRT_x86.msm Errors: 5 ModuleInstallExecuteSequence InstallExecuteSequence Modkeys: SxsInstallCA DBKeys: SxsInstallCA 5 ModuleInstallExecuteSequence InstallExecuteSequence Modkeys: SxsUninstallCA DBKeys: SxsUninstallCA 4 _Validation _Validation Modkeys: _Validation Nullable DBKeys: _Validation Nullable 4 _Validation _Validation Modkeys: CustomAction Type DBKeys: CustomAction Type 4 _Validation _Validation Modkeys: File Sequence DBKeys: File Sequence Start of Media 2644 The final .msi file appears to work fine as long as I can tell. Error type 4 is msmErrorTableMerge and type 5 is msmErrorResequenceMerge, but I don't know enough of the msi technology to tell if those errors are important or not. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On 2009-10-31 19:21 PM, Wolodja Wentland wrote: On Sat, Oct 31, 2009 at 18:29 -0500, Peng Yu wrote: And I always put a single class in a file. Why? What do you gain by that? While it's never a good idea to follow the rule slavishly, it's often a good idea. Many classes are themselves a semantic unit of functionality enough to justify their own module. I've certainly seen the rule overapplied, though. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Are *.pyd's universal?
On Sat, 31 Oct 2009 23:58:33 +1300, Lawrence D'Oliveiro wrote: In message mailman.2365.1256979069.2807.python-l...@python.org, Albert Hopkins wrote: On Sat, 2009-10-31 at 21:32 +1300, Lawrence D'Oliveiro wrote: In message 6e603d9c-2be0-449c-9c3c-bab49e09e...@13g2000prl.googlegroups.com, Carl Banks wrote: Modules will sometimes find themselves on the path in Windows, so the fact that Windows performs a library search on the path is quite significant. Why is it only Windows is prone to this problem? I question your assumption. DLL hell is merely a platform-specific name for a particular variety of a broader class of problems, namely dependency conflicts and the bootstrapping problem. It's not even specific to software -- bootstrapping problems are well known in many fields of endeavour: before you can make the tools to make things, you need to make the tools to make the tools... It is far from true to say that Windows is the only system subject to this problem. http://en.wikipedia.org/wiki/Dependency_hell Python, like most (all?) programming languages, has it's own version of dependency hell, namely circular imports: module A depends on module B, which depends on module C, which depends on module A... Python also has a second DLL Hell, as many newbies discover: shadowing standard library modules. Create a module (say) random.py in the current directory, and then try to import the standard library random. This is a form of DLL Hell, because Python uses standard library modules dynamically, importing them at runtime. One solution to dependency conflicts and circular dependencies is to avoid dependencies altogether. At the cost of disk space and memory, use static linking and give up the benefits of dynamic libraries. Platforms that encourage static linking avoid the DLL conflicts, but at the cost of increased memory and storage usage, and static applications need to be upgraded individually instead of merely upgrading the shared library. I think as someone pointed out earlier, in Unix-like operating systems, a regular library's file name starts with lib, e.g. libcrypt.so. So this would not conflict with Python's crypt.so. But it would conflict with a Python module libcrypt.so if the PYTHONPATH and the OS's shared library path coincided. I just checked my Debian installation: l...@theon:~ find /lib /usr/lib -name \*.so -a -not -name lib\* -print | wc -l 2950 l...@theon:~ find /lib /usr/lib -name \*.so -print | wc -l 4708 So 63% of the shareable libraries on my system have names NOT beginning with lib. 53% on my system. This just goes to show that even Linux developers often don't bother with the conventions for their platforms. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 7:21 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 18:29 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 5:45 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. If two functions are too long to put in file, I generally put them in two different files. If it should ever happen that two functions are too long to put in a single file you should refactor your code. It is usually a good idea of breaking problems down into single steps (ie functions) so you never end up with a 5000 SLOC *function*. My definition of long is more than one screen. How do functions of this length enhance the readability of your source code? If the code is of one screen, you can easily see what it does without having to scroll back and forth. And I always put a single class in a file. Why? What do you gain by that? It makes me easier to look for an class. I can just search the filename to get a class. By looking at the packages imported in the file, I can easily see what packages a class depends. If there are multiple classes in a file, I will not know which packages a class actually depends on. Suppose that I have many functions in one file, it is not clear to see how many functions are in the file at first glance. Use a better editor/IDE for that. What editor you use? I use vim. I'm sure there is a way to configure vim to fold the definition of a class. But I don't use it because I feel folding and unfolding code is not convenient. [snip] I thought about answering your post in greater detail, but i would like to evaluate your style of work first. Is there any place where I can have a look at some of your source code? It would be perfect if it is a medium sized project with said unit tests, packages and function-modules and the rest you described. I just started writing python code. So I don't have much code to show you now. But I have written a project of 25,000 lines of code in C++. In this project, I always have a file for a class. My directory structure looks like the following (toward the end). But having this structure it is every easy to navigate to any class or function. Please let me know if you need any more information. src/ has all the source code and testing code. Because I usually need to change source code and the corresponding test code at the same time, I put them close to each other. include/ has links to all the header files and maintains the directory structure (include/ is generated automatically based on the content of src/). All .cpp files are linked to lib/, where the library file is made. The unit test for divide is in main.cpp. | |-- divide.cpp | |-- divide.hpp | `-- main.cpp When test cases become big, I separate them into multiple main.cpp files like below. | |-- half | | |-- Makefile | | |-- cap | | | |-- Makefile | | | `-- main.cpp | | |-- half.hpp | | |-- is_interleaved | | | |-- Makefile | | | `-- main.cpp | | |-- less_than | | | |-- Makefile | | | `-- main.cpp | | `-- main | | |-- Makefile | | `-- main.cpp The namespace is defined accordingly. For example, class divide.hpp is in numerical/divide.hpp, therefore, I use numerical::divide to refer it. ### example directory structure . |-- include | `-- numerical | |-- divide.hpp - ../../src/divide/divide.hpp | |-- interval | | |-- combine_half.hpp - ../../../src/interval/combine_half/combine_half.hpp | | |-- half.hpp - ../../../src/interval/half/half.hpp | | |-- linear.hpp - ../../../src/interval/linear/linear.hpp | | `-- rotated.hpp - ../../../src/interval/rotated/rotated.hpp | `-- smart_increment.hpp - ../../src/smart_increment/smart_increment.hpp |-- lib | |-- Makefile | |-- libnumerical.so - libnumerical.so.1 | |-- libnumerical.so.1 - libnumerical.so.1.0.0 | `-- numerical | `-- divide.cpp - ../../src/divide/divide.cpp `-- src |-- Makefile |-- divide | |-- Makefile | |-- divide.cpp | |-- divide.hpp | `-- main.cpp |-- interval | |-- Makefile | |-- combine_half | | |-- Makefile | | |-- combine_half.hpp | | `-- main.cpp | |-- half | | |-- Makefile | | |-- cap | | | |-- Makefile | | | `-- main.cpp | | |-- half.hpp | | |-- is_interleaved | | | |-- Makefile | | | `-- main.cpp | | |-- less_than | | | |-- Makefile | | | `--
Re: import bug
On Sat, 31 Oct 2009 16:27:20 +, kj wrote: 1) it's a bad idea to name your own modules after modules in the stdlib Obviously, since it leads to the headaches this thread illustrates. But there is nothing intrisically wrong with it. The fact that it is problematic in Python is a design bug, plain and simple. There's no rational basis for it, Incorrect. Simplicity of implementation and API is a virtue, in and of itself. The existing module machinery is quite simple to understand, use and maintain. Dealing with name clashes doesn't come for free. If you think it does, I encourage you to write a patch implementing the behaviour you would prefer. In addition, there are use-cases where the current behaviour is the correct behaviour. Here's one way to backport (say) functools to older versions of Python (untested): # === functools.py === import sys if sys.version = '2.5': # Use the standard library version if it is available. old_path = sys.path[:] del sys.path[0] # Delete the current directory. from functools import * sys.path[:] = old_path # Restore the path. else: # Backport code you want. pass and represents an unreasonable demand on module writers, since contrary to the tight control on reserved Python keywords, there does not seem to be a similar control on the names of stdlib modules. What if, for example, in the future it was decided that my_favorite_module name would become part of the standard library? This alone would cause code to break. Not necessarily. Obviously your module my_favorite_module.py isn't calling the standard library version, because it didn't exist when you wrote it. Nor are any of your callers. Mere name clashes alone aren't necessarily an issue. One problem comes about when some module you import is modified to start using the standard library module, which conflicts with yours. Example: You have a collections module, which imports the standard library stat module. The Python standard library can safely grow a collections module, but what it can't do is grow a collections module *and* modify stat to use that. But in general, yes, you are correct -- there is a risk that future modules added to the standard library can clash with existing third party modules. This is one of the reasons why Python is conservative about adding to the std lib. In other words, yes, module naming conflicts is the Python version of DLL Hell. Python doesn't distinguish between my modules and standard modules and third party modules -- they're all just modules, there aren't three different implementations for importing a module and you don't have to learn three different commands to import them. But there is a downside too: if you write import os Python has no possible way of knowing whether you mean the standard os.py module or your own os.py module. Of course, Python does expose the import machinary to you. If avoiding standard library names is too much a trial for you, or if you are paranoid and want to future-proof your module against changes to the standard library (a waste of time in my opinion), you can use Python's import machinery to build your own system. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
Peng Yu wrote: On Sat, Oct 31, 2009 at 5:45 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 4:14 PM, Robert Kern robert.k...@gmail.com wrote: [ snip ] I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. snip One advantage is on refactoring. When each function has its own file, I can change variable names, etc., for a give function without worrying accidentally change variable names in other functions. When I find a function is more appropriate to put in another namespace, I can just move the file around. Variables in a function are already private. How can the names in one function be affected by other functions in the same module? DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, 31 Oct 2009 18:29:35 -0500, Peng Yu wrote: If two functions are too long to put in file, I generally put them in two different files. If two functions are too long for a single file, the functions are too big and need to be broken up into ten or thirty sub-functions each! Ideally, no function should be more than ten or twenty lines (plus docstring), certainly no more than a page. In a language like Python that is so compact, monster functions that are hundreds of lines long is almost certainly inexcusable. And I always put a single class in a file. An unnecessary and silly restriction. It is reasonable for large complicated classes, but not a rule for all classes, some of which might be as small as two lines. Suppose that I have many functions in one file, it is not clear to see how many functions are in the file at first glance. So what? Why is it import to see how many functions are in the file? If I put each function in its own file, just by looking at the directory structure, I can easily see how many functions there are. Why do you care how many functions there are? One advantage is on refactoring. When each function has its own file, I can change variable names, etc., for a give function without worrying accidentally change variable names in other functions. Do you understand that each function has it's own local namespace? Unless you are foolish enough to use global variables for everything, you can refactor any given function without effecting other functions in the same file. When I find a function is more appropriate to put in another namespace, I can just move the file around. A module is a namespace. Another advantage is on testing. I can have associated test dir for each class or function. By this way I can easily locate the definition and the test to track any potential problems. You can do this when functions share the same file. You can use package rather than module to group semantic related classes and functions. Python makes available many namespaces: Function Module Package You are artificially restricting yourself to use: Function = Module Package and that's supposed to be an advantage??? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, 31 Oct 2009 20:03:29 -0500, Peng Yu wrote: If it should ever happen that two functions are too long to put in a single file you should refactor your code. It is usually a good idea of breaking problems down into single steps (ie functions) so you never end up with a 5000 SLOC *function*. My definition of long is more than one screen. How do functions of this length enhance the readability of your source code? If the code is of one screen, you can easily see what it does without having to scroll back and forth. Far enough, but you exchange scrolling back and forth from function to function with tabbing through editor tabs from file to file. I don't see that this is an advantage. You also complicate calling functions. Instead of: def parrot(): spam() ham() cheeseshop() you need: from spam import spam from ham import ham from import cheeseshop def parrot(): spam() ham() cheeseshop() This is not an advantage! -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, 31 Oct 2009 16:53:50 -0500, Peng Yu wrote: I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). When one class per module is strictly enforced, there will be no need to have different capitalization conventions for modules and classes. Developers should be able to tell whether it is a class or a module from the context. Classes and modules are first-class objects in Python, so you can't necessarily tell what they are from context. I frequently have code like this: def verify(test_func, objects_to_process, expected_results): for obj, result in zip(objects_to_process, expected_results): print Testing %r... % obj, r = test_func(obj) if r == result: print verified else: print expected %r but got %s % (result, r) objects_to_process could be a list of floats, strings, functions, modules, or anything else. Having a naming convention is still useful for distinguishing (say) factory functions from classes, or modules from classes. In my question, module A and B exist just for the sake of implementation. Even if I have module A and B, I don't want the user feel the existence of module A and B. I want them feel exact like class A and B are defined in module 'test' instead of feeling two modules A and B are in package 'test'. Inside test/__init__.py: from A import A # class A from file A.py from B import B # class B from file B.py or better still: from a import A # class A from file a.py from b import B # class B from file b.py I know that module names should be in lower cases, in general. However, it is OK to have the module name capitalized in this case since the end users don't see them. Of course they do. I looked at python library, there are quite a few __init__.py files are not empty. In fact, they are quite long. I agree with you that '__init__.py' should not be long. But I'm wondering why in python library __init__.py are quite long. Define quite long. In Python 2.6, I have: [st...@sylar python2.6]$ for file in */__init__.py; do echo $file `cat $file | wc -l` ; done bsddb/__init__.py 450 compiler/__init__.py 29 ctypes/__init__.py 546 curses/__init__.py 59 distutils/__init__.py 26 email/__init__.py 123 encodings/__init__.py 157 hotshot/__init__.py 78 idlelib/__init__.py 1 json/__init__.py 318 lib2to3/__init__.py 1 logging/__init__.py 1490 multiprocessing/__init__.py 271 sqlite3/__init__.py 24 test/__init__.py 1 wsgiref/__init__.py 23 xml/__init__.py 47 With the exception of logging, I don't see any of those as quite long. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Looking for help getting tkinter to work.
I tried to compile Python and Tcl/Tk on Linux using the following files: Python-3.1.1.tar.gz tcl8.5.7-src.tar.gz Cannot get tkinter to work after compiling installing Tcl/Tk. I get the following error after compiling Python: Python build finished, but the necessary bits to build these modules were not found: _tkinter To find the necessary bits, look in setup.py in detect_modules() for the module's name. Are the above files the correct versions to get tkinter to work? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 10:03 PM, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Sat, 31 Oct 2009 16:53:50 -0500, Peng Yu wrote: I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). When one class per module is strictly enforced, there will be no need to have different capitalization conventions for modules and classes. Developers should be able to tell whether it is a class or a module from the context. Classes and modules are first-class objects in Python, so you can't necessarily tell what they are from context. I frequently have code like this: def verify(test_func, objects_to_process, expected_results): for obj, result in zip(objects_to_process, expected_results): print Testing %r... % obj, r = test_func(obj) if r == result: print verified else: print expected %r but got %s % (result, r) This example doesn't invalidate my statement. When I say Developers should be able to tell whether it is a class or a module from the context, I mean the case of defining them or creating objects. In the above case, you still can enforce one class/function per module. objects_to_process could be a list of floats, strings, functions, modules, or anything else. Having a naming convention is still useful for distinguishing (say) factory functions from classes, or modules from classes. In my question, module A and B exist just for the sake of implementation. Even if I have module A and B, I don't want the user feel the existence of module A and B. I want them feel exact like class A and B are defined in module 'test' instead of feeling two modules A and B are in package 'test'. Inside test/__init__.py: from A import A # class A from file A.py from B import B # class B from file B.py I can not use the above approach as I mentioned its problem in my previous message. or better still: from a import A # class A from file a.py from b import B # class B from file b.py This artificially introduces the constraint that the file name can not be the same as the class/function name. There is no constraint like this if I can C++. I know that module names should be in lower cases, in general. However, it is OK to have the module name capitalized in this case since the end users don't see them. Of course they do. This sentence is confusing. Can you spell out what you mean? I looked at python library, there are quite a few __init__.py files are not empty. In fact, they are quite long. I agree with you that '__init__.py' should not be long. But I'm wondering why in python library __init__.py are quite long. Define quite long. In Python 2.6, I have: [st...@sylar python2.6]$ for file in */__init__.py; do echo $file `cat $file | wc -l` ; done bsddb/__init__.py 450 compiler/__init__.py 29 ctypes/__init__.py 546 curses/__init__.py 59 distutils/__init__.py 26 email/__init__.py 123 encodings/__init__.py 157 hotshot/__init__.py 78 idlelib/__init__.py 1 json/__init__.py 318 lib2to3/__init__.py 1 logging/__init__.py 1490 multiprocessing/__init__.py 271 sqlite3/__init__.py 24 test/__init__.py 1 wsgiref/__init__.py 23 xml/__init__.py 47 With the exception of logging, I don't see any of those as quite long. I have defined 'long' in one of my previous message. I consider a file long, when it does not fit in one or two screen. Basically, I want to get a whole picture of the file after glancing of the file. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 9:42 PM, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Sat, 31 Oct 2009 20:03:29 -0500, Peng Yu wrote: If it should ever happen that two functions are too long to put in a single file you should refactor your code. It is usually a good idea of breaking problems down into single steps (ie functions) so you never end up with a 5000 SLOC *function*. My definition of long is more than one screen. How do functions of this length enhance the readability of your source code? If the code is of one screen, you can easily see what it does without having to scroll back and forth. Far enough, but you exchange scrolling back and forth from function to function with tabbing through editor tabs from file to file. I don't see that this is an advantage. You also complicate calling functions. Instead of: def parrot(): spam() ham() cheeseshop() you need: from spam import spam from ham import ham from import cheeseshop def parrot(): spam() ham() cheeseshop() This is not an advantage! I would say this is the disadvantage of python, if there is no walkaround to avoid using 'from spam import spam'. As this can be handled in C++ with walkaround. So far the best solution is: Inside test/__init__.py: from a import A # class A from file a.py from b import B # class B from file b.py However, this is not satisfactory enough because this artificially introduces the constraint that the file name can not be the same as the class/function name. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
Peng Yu wrote: I have defined 'long' in one of my previous message. I consider a file long, when it does not fit in one or two screen. Basically, I want to get a whole picture of the file after glancing of the file. I think you are going to have to get used to the fact that you have very strange personal preferences and that Python is designed for the vast majority of programmers who do not share them. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 9:34 PM, Steven D'Aprano st...@remove-this-cybersource.com.au wrote: On Sat, 31 Oct 2009 18:29:35 -0500, Peng Yu wrote: If two functions are too long to put in file, I generally put them in two different files. If two functions are too long for a single file, the functions are too big and need to be broken up into ten or thirty sub-functions each! Ideally, no function should be more than ten or twenty lines (plus docstring), certainly no more than a page. In a language like Python that is so compact, monster functions that are hundreds of lines long is almost certainly inexcusable. And I always put a single class in a file. An unnecessary and silly restriction. It is reasonable for large complicated classes, but not a rule for all classes, some of which might be as small as two lines. Suppose that I have many functions in one file, it is not clear to see how many functions are in the file at first glance. So what? Why is it import to see how many functions are in the file? If I put each function in its own file, just by looking at the directory structure, I can easily see how many functions there are. Why do you care how many functions there are? Because I want to easily see what functions are there. One advantage is on refactoring. When each function has its own file, I can change variable names, etc., for a give function without worrying accidentally change variable names in other functions. Do you understand that each function has it's own local namespace? Unless you are foolish enough to use global variables for everything, you can refactor any given function without effecting other functions in the same file. When I find a function is more appropriate to put in another namespace, I can just move the file around. A module is a namespace. This is a constrain imposed by python. C++ does not have this constraint, so I can have each class in a file without any complication in calling classes. Because of this constraint in python. I have do something from spam import spam or call spam.spam. Another advantage is on testing. I can have associated test dir for each class or function. By this way I can easily locate the definition and the test to track any potential problems. You can do this when functions share the same file. You can use package rather than module to group semantic related classes and functions. Python makes available many namespaces: Function Module Package You are artificially restricting yourself to use: Function = Module Package and that's supposed to be an advantage??? Since Module = file, by making Function = Module and Class = Module, it simplifies the search of a function and a class. I also put the testing code along with the module, which make it easier to move module across packages (when I do refactoring, sometime I found some module is not appropriate to put in a package anymore, so I need to move it to a better package). -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 9:18 PM, Dave Angel da...@ieee.org wrote: Peng Yu wrote: On Sat, Oct 31, 2009 at 5:45 PM, Wolodja Wentland wentl...@cl.uni-heidelberg.de wrote: On Sat, Oct 31, 2009 at 16:53 -0500, Peng Yu wrote: On Sat, Oct 31, 2009 at 4:14 PM, Robert Kern robert.k...@gmail.com wrote: [ snip ] I know that multiple classes or functions are typically defined in one file (i.e. module in python). However, I feel this make the code not easy to read. Therefore, I insist on one class or function per file (i.e module in python). Are you serious? Do you *really* put each function in its own file? How exactly does this enhance the readability of the source code? Especially if you compare that to a (sic!) modularisation scheme that groups classes and functions together by task or semantic relatedness. snip One advantage is on refactoring. When each function has its own file, I can change variable names, etc., for a give function without worrying accidentally change variable names in other functions. When I find a function is more appropriate to put in another namespace, I can just move the file around. Variables in a function are already private. How can the names in one function be affected by other functions in the same module? You misunderstood me. If there are multiple functions or classes in a file, when I change variables in a function/class, I have to make sure that they are not in other functions or classes. This makes the refactoring process tedious. If I have a single class/function in a file, I can safely change variable names without worrying broken other classes or functions. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
On Sat, Oct 31, 2009 at 10:35 PM, Robert Kern robert.k...@gmail.com wrote: Peng Yu wrote: I have defined 'long' in one of my previous message. I consider a file long, when it does not fit in one or two screen. Basically, I want to get a whole picture of the file after glancing of the file. I think you are going to have to get used to the fact that you have very strange personal preferences and that Python is designed for the vast majority of programmers who do not share them. So python would not be able to accommodate my preference one class/function per file? I.e., I have to use something like 'from spam import spam' or 'spam.spam()', or accept that the filename is not the same as the class/function name. Inside test/__init__.py: from a import A # class A from file a.py from b import B # class B from file b.py -- http://mail.python.org/mailman/listinfo/python-list
Re: How to import only one module in a package when the package __init__.py has already imports the modules?
Peng Yu wrote: On Sat, Oct 31, 2009 at 10:35 PM, Robert Kern robert.k...@gmail.com wrote: Peng Yu wrote: I have defined 'long' in one of my previous message. I consider a file long, when it does not fit in one or two screen. Basically, I want to get a whole picture of the file after glancing of the file. I think you are going to have to get used to the fact that you have very strange personal preferences and that Python is designed for the vast majority of programmers who do not share them. So python would not be able to accommodate my preference one class/function per file? I.e., I have to use something like 'from spam import spam' or 'spam.spam()', or accept that the filename is not the same as the class/function name. Inside test/__init__.py: from a import A # class A from file a.py from b import B # class B from file b.py If you are going to expose symbols in your __init__.py, they should not have the same name as any of the modules in the package. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
