ANN: Python training, 2006 Feb 1-3, San Francisco
What: Python Programming I: Introduction to Python When: February 1-3, 2006 Where: San Francisco, CA, USA Web:http://cyberwebconsulting.com Need to get up-to-speed with Python as quickly as possible? Come join us in beautiful Northern California for another rigorous Python training event taught by software engineer, Core Python Programming author, and technical instructor Wesley Chun. This is an intense introduction to Python programming geared towards those who have some proficiency in another high-level language. Topics include: * Syntax, Data Types, Operators, and Methods * Python's Objects and Memory Model * Errors and Exception Handling * Flow Control (Loops and Conditionals) * Writing Optimized Python * Files and Input/Output * Functions and Functional Programming Aspects * Modules and Packages * OOP: Classes, Methods, and Class Instances * OOP: Class Customization, Inheritance * Execution Environment * Operating System Interface * Advanced Topics and Python Updates This course will take place near the San Francisco International Airport at the: Staybridge Suites San Francisco Airport 1350 Huntington Ave San Bruno, CA 94066 USA +1-650-588-0770 VISITORS: free transportation to/from the San Francisco International airport LOCALS and VISITORS: easy access to public transit (BART [across the street!], CalTrain, SamTrans) can help you get all over the San Francisco Bay Area Discounts are available for multiple registrations as well as teachers/students. For more information and registration, go to http://cyberwebconsulting.com and click on the Python Training link. Unlike previous courses, we are limiting enrollment to a maximum of 15 attendees. If you have any questions, feel free to contact us at cyberweb-at-rocketmail.com. For those who are interested in more advanced Python topics, we'reoffering a follow-on course late Spring 2006 (most likely May). Also, if there is sufficient interest, we may hold another one of these Intro to Python courses down in Silicon Valley in April; contact me directly if you're interested in this location. Note: i will only send out ONE MORE REMINDER in January... yeah, i don't like spam either. :-) cheers, -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Core Python Programming, Prentice Hall, (c)2006,2001 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations.html
[ANN] Python-OpenID 1.0
It is with great pleasure that JanRain, Inc. announces version 1.0 of the Python OpenID library. This library contains packages to support both OpenID consumers (relying parties) and servers. For back-end storage, it supports a variety of methods, including flat file, SQL, and MemCached. In our own work on making applications OpenID enabled, we've been reminded that every web framework is different. For that reason we've strived to make this library general enough to fit in to any Python web application. We also like to think the API is simple to follow. Let us know how it works for you. Home: http://openidenabled.com/openid/libraries/python License: LGPL Download: http://openidenabled.com/openid/libraries/python/downloads/ Docs: http://openidenabled.com/python-openid-docs/1.0.0/ Requires: Python (versions 2.2 through 2.4) What is this OpenID Thing Anyway? OpenID is a decentralized identity system that provides authentication for web applications, i.e. single sign-on for the web. See http://openid.net/ If you're interested in OpenID but this library isn't quite what you've been waiting for for, keep your eye on http://openidenabled.com. There's more coming. Share and Enjoy, - the OpenID Team at JanRain [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations.html
[ANNOUNCE] Twenty-seventh release of PythonCAD now available
Hi. I'm pleased to announce the twenty-seventh development release of PythonCAD, a CAD package for open-source software users. As the name implies, PythonCAD is written entirely in Python. The goal of this project is to create a fully scriptable drafting program that will match and eventually exceed features found in commercial CAD software. PythonCAD is released under the GNU Public License (GPL). PythonCAD requires Python 2.2 or newer. The interface is GTK 2.0 based, and uses the PyGTK module for interfacing to GTK. The design of PythonCAD is built around the idea of separating the interface from the back end as much as possible. By doing this, it is hoped that both GNOME and KDE interfaces can be added to PythonCAD through usage of the appropriate Python module. Addition of other PythonCAD interfaces will depend on the availability of a Python module for that particular interface and developer interest and action. The twenty-seventh release contains primarily bug fixes and internal code enhancements. A long-standing interface problem where the display of selected entities was not clear has been fixed. When you select an entity it is redrawn in a highlighting color, making it clear which entities are selected at any one time. Also, the ability to deselect a selected entity has been added to the interface. The bug fixes included in this release address a few problems introduced in the previous release as well as various older issues. A mailing list for the development and use of PythonCAD is available. Visit the following page for information about subscribing and viewing the mailing list archive: http://mail.python.org/mailman/listinfo/pythoncad Visit the PythonCAD web site for more information about what PythonCAD does and aims to be: http://www.pythoncad.org/ Come and join me in developing PythonCAD into a world class drafting program! Art Haas -- Man once surrendering his reason, has no remaining guard against absurdities the most monstrous, and like a ship without rudder, is the sport of every wind. -Thomas Jefferson to James Smith, 1822 -- http://mail.python.org/mailman/listinfo/python-announce-list Support the Python Software Foundation: http://www.python.org/psf/donations.html
Re: efficient 'tail' implementation
As long as memory mapped files are available, the fastest method is to map the whole file into memory and use the mappings rfind method to search for an end of line. The following code snippets may be usefull: reportFile = open( filename ) length = os.fstat( reportFile.fileno() ).st_size if length == 0: # Don't map zero length files, windows will barf continue try: mapping = mmap.mmap( reportFile.fileno(), length, mmap.MAP_PRIVATE, mmap.PROT_READ ) except AttributeError: mapping = mmap.mmap( reportFile.fileno(), 0, None, mmap.ACCESS_READ ) Then you can use mapping.rfind( os.linesep ) to find the end of the but last line and so on. This is very fast, because nearly all work is done by are rfind, which is implemented in C and the OS' paging logic. HTH, Gerald [EMAIL PROTECTED] schrieb: Mike Meyer wrote: It would probably be more efficient to read blocks backwards and paste them together, but I'm not going to get into that. That actually is a pretty good idea. just reverse the buffer and do a split, the last line becomes the first line and so on. The logic then would be no different than reading from beginning of file. Just need to keep the last half line of the reversed buffer if the wanted one happens to be across buffer boundary. -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao Language v.0.9.6-beta is release!
Op 2005-12-07, Zeljko Vrba schreef [EMAIL PROTECTED]: On 2005-12-07, Antoon Pardon [EMAIL PROTECTED] wrote: What I don't understand is, that most people who have a problem with scope by indentation, want to introduce braces. I think braces are the worst solution. Braces are very convenient to match block start and end. Other conventions can be just as convenient. Open a C program in the VI editor, and press % in command mode on some brace.. It will take you to its matching brace. How do you do something like that with python code (or any code that is based purely on indentation..) Not my problem, since I don't suggest pure indentation is the way to go. I just think braces are the worst solution for it, as python is concerned. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao Language v.0.9.6-beta is release!
Op 2005-12-07, Steven D'Aprano schreef [EMAIL PROTECTED]: On Wed, 07 Dec 2005 15:26:59 +, Zeljko Vrba wrote: Braces are very convenient to match block start and end. Open a C program in the VI editor, and press % in command mode on some brace.. It will take you to its matching brace. How do you do something like that with python code (or any code that is based purely on indentation..) (1) You don't need to, because you can *see* where the indentation changes, so you don't need to rely on your editor counting for you. But you can't alway easily discern by how much. (2) And if you do need to, then you should use a smarter editor that understands indentation levels, not just braces. Braces are superfluous if you use consistent indentation, and indentation is superfluous -- to the compiler -- if you use braces. But indentation is *not* superfluous to the human eye: we can parse indentation very easily, but nested braces/brackets only with great difficulty. That's why programmers in languages that ignore indentation still indent their code, or at least the sensible ones do. But sometimes you mess up and your code is no longer indented as it should. If you marked the end of the indentations, you can easily correct this. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: sql escaping module
David Bear [EMAIL PROTECTED] wrote:
Being new to pgdb, I'm finding there are lot of things I don't understand
when I read the PEP and the sparse documentation on pgdb.
I was hoping there would be a module that would properly escape longer text
strings to prevent sql injection -- and other things just make sure the
python string object ends up being a properly type for postgresql. I've
bought 3 books on postgresql and none of th code samples demonstrate this.
All of the Python database modules will do this protection for you.
Example:
db = psycopg2.connect(database='dbname')
c = db.cursor()
c.execute( INSERT INTO table1 VALUES (%s,%s,%s);, (var1, var2, var3) )
Note that I have used a comma, not the Python % operator, and I have not
done any quoting in the query. By doing that, I am instructing the
database module to do whatever protective quoting may be required for the
values I have passed, and substitute the quoted values into the string.
As long as you use that scheme, you should be safe from injection. It's
only when people try to do it themselves that they get in trouble, as in:
c.execute( INSERT INTO table1 VALUES ('%s','%s','%s'); % (var1, var2,
var3) ) # THIS IS WRONG
--
- Tim Roberts, [EMAIL PROTECTED]
Providenza Boekelheide, Inc.
--
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RE: hi i have some doubts on a volume and the file system
[EMAIL PROTECTED] i want to check the position of a volume in a particular drive. say for example in a disk i have 3 different drives: C:\ , D:\ and E:\. Now if i want to check what position is the D:\ in, how can i write the code. Means whether its in a 0th position or 1st position or a 2nd position. Is there any way using win32api or win32com. if i want to check a particular volume is a logical, or a primary one , what is the method i have to use? does it can also be done through win32api. Well, this page suggests that it's possible using WMI: http://www.microsoft.com/technet/scriptcenter/resources/qanda/may05/hey0 523.mspx and, using the WMI module from here: http://timgolden.me.uk/python/wmi.html this bit of code seems to give you what you want. code import wmi c = wmi.WMI () for physical_disk in c.Win32_DiskDrive (): for partition in physical_disk.associators (Win32_DiskDriveToDiskPartition): for logical_disk in partition.associators (Win32_LogicalDiskToPartition): print physical_disk.Caption, partition.Caption, logical_disk.Caption /code Obviously, I've just printed the Caption, but you could pick up whatever information you wanted from the disk, partition logical_disk objects. If you just print the object itself, it will give you all its fields and values. By the way, thanks for the question. I've never come across a meaningful example of WMI associators before, although I've had the code in the module since the first version. TJG This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk -- http://mail.python.org/mailman/listinfo/python-list
Re: python24.dll and encodings ?
Bugs wrote: I believe I read in a relatively recent thread that the reason python24.dll is so large compared to previous releases is that all the language encodings are linked into the library? Not only that (but also). In addition, it also contains modules that were previously implemented as separate .pyd files (_csv, _sre, _symtable, _winreg, datetime, mmap, parser). Are there any plans for future releases to split the encodings out so that, for example, if someone wanted to make a smaller executable using py2exe without all the language encodings, they could do so? I previously said that I would do such a thing if somebody provided a specification other than split out the encodings. I.e. write a PEP that specifies how to determine whether an extension module should be included into pythonxy.dll, and when it should not; this specification should allow to reason about modules that haven't yet been contributed. The PEP should be accompanied with an implementation, i.e. a set of patches to PCbuild. Then, the patch should be discussed, and find support in the community. I suppose one could always compile their own version of the python24.dll but for those of us that are compiler-challanged, splitting out the encodings would be nice. Is that even feasible? Technically, yes. However, somebody needs to take the lead. Regards, Martin -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
[EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: I suspect I'd have a harder time living without the sys module than with many of the builtins. Then there's os, re, math, ... Some modules, like thread and sys, have to be linked into the interpreter. Are they core or add on? Once you start migrating stuff from the add on manual (Library Reference) to the core manual (Language Reference), where do you stop? I think a natural dividing line is import. If you import it, it is in the Library refrence. Exactly. I'm surprised this is even open to debate. Any built-in which will work without an import statement - no matter how it's implemented - should be documented as if it was part of the core language. And anything you have to explicitly ask for using import, should be in the library reference under the name of the module or package you're importing. In terms of knowing where to look for information on a feature, this is the most sensible approach. In no other language would I look to the library reference for something which does not appear on the surface to come from a library. As an aside, personally I rarely touch the sys module. I use re, random, threading, and even xml.dom.minidom more than sys. -- Ben Sizer -- http://mail.python.org/mailman/listinfo/python-list
pyparsing with nested table
using pyparsing to deal with nested tables , wanna keep table's
structure and propertys .
but program was chunked with the /td tag of inner table.
have any ideas?
here's the program
from pyparsing import *
mytable =
table id=leftpage_table width=156 border=0 cellspacing=0
cellpadding=0
tr id=trtd height=24
td width=153 background=images/bt_kind.gif align=center
class=left_menusystem/td
/tr
tr id=trtd_down height=20
td id=trtd_downtable id=inner_lefgpage_table width=100%
height=100% border=0 cellspacing=0 cellpadding=0
tr id=inner_trtd height=20
td background=images/bt_class.gif align=centerart/td
/tr
tr
td background=images/bt_class.gif align=centerart/td
/tr
/table/td
/tr
/table
startTag = Literal()
endTag = Literal()
idPattern = CaselessLiteral(id).suppress() + Literal(=).suppress()
+ ( quotedString.copy().setParseAction( removeQuotes ) |
Word(srange([a-zA-Z0-9_~])))
attrPattern = Combine(Word(alphanums + _) + Literal(=) + (
quotedString | Word(srange([a-zA-Z0-9_~:@#;?/\.]
tablePattern = Forward()
def getItemCloseTag(x):
itemCloseTag = Combine(startTag + Literal(/) + CaselessLiteral(x)
+ endTag).suppress()
return itemCloseTag
def getItemStartTag(x):
itemStartTag = startTag.suppress() +
Keyword(x,caseless=True).suppress() + Group(ZeroOrMore(idPattern)) +
Group(ZeroOrMore(attrPattern)) + endTag.suppress()
return itemStartTag
def getItemPattern(x):
tCloseTag = getItemCloseTag(x)
itemPattern = getItemStartTag(x) + Group(ZeroOrMore(tablePattern))
+ Group(SkipTo(tCloseTag)) + tCloseTag
return itemPattern
def getMultiLevelPattern(x,y):
tCloseTag = getItemCloseTag(x)
itemPattern = getItemStartTag(x) + Group(OneOrMore(y)) + tCloseTag
return itemPattern
tdPattern = getItemPattern(x='td')
trPattern = getMultiLevelPattern('tr',tdPattern)
tablePattern = getMultiLevelPattern('table',trPattern)
t = tablePattern
for toks,strt,end in t.scanString(mytable):
print toks.asList()
OutPut:
[['leftpage_table'], ['width=156', 'border=0', 'cellspacing=0',
'cellpadding=0'], [['trtd'], ['height=24'], [[], ['width=153',
'background=images/bt_kind.gif', 'align=center',
'class=left_menu'], [], ['system']], ['trtd_down'], ['height=20'],
[['trtd_down'], [], [], ['table id=inner_lefgpage_table width=100%
height=100% border=0 cellspacing=0 cellpadding=0\ntr
id=inner_trtd height=20\n td
background=images/bt_class.gif align=centerart']], [], [], [[],
['background=images/bt_class.gif', 'align=center'], [], ['art'
--
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Re: Is Python string immutable?
Frank Potter wrote: Thank you very much. Steve Holden, I post my soucecode at my blog here: http://hiparrot.wordpress.com/2005/12/08/implementing-a-simple-net-spider/ http://hiparrot.wordpress.com/2005/12/08/implementing-a-simple-net-spider/ I wish you can read and give me some suggestion. Any comments will be appreciated. Before any intensive scrutiny of the code perhaps you can answer a few questions. 1. Are you absolutely sure you have published the code you are running? The code you reference has indentation problems that give syntax errors. 2. Why do you continually create new threads when you could have a fixed set of threads sharing a list of URLs to scan? 3. What steps have you taken to ensure that the program does indeed perform according to its specifications? It seems to me that this code is a Java program transliterated into Python. A more natural way to express the algorithm would be for a number of worker threads to share Queue.Queue of URLs to be visited. The only other data structure that would then need locking would be a dictionary of URLs that had already been considered. Overall you appear to be spending large amounts of time locking and unlocking things, and creating threads unnecessarily, but you don't claim that the algorithm is particularly refined, and it shouldn;t affect memory usage. However, I would like to be sure that the excessive memory usage *is* indeed something to do with your program, as I contend, and not some buggy aspect of threading, so I await your answers with interest. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Mutability of function arguments?
ex_ottoyuhr wrote:
I'm trying to create a function that can take arguments, say, foo and
bar, and modify the original copies of foo and bar as well as its local
versions -- the equivalent of C++ funct(foo, bar).
This is already what you have. In Python, all you have are references to
objects, there is no local version.
I've looked around on this newsgroup and elsewhere, and I gather that
this is a very common concern in Python, but one which is ordinarily
answered with No, you can't. Neat, huh?
Pardon ???
def appendToList(aList, aValue):
... aList.append(aValue)
...
mylist = range(10)
mylist
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
appendToList(mylist, 42)
mylist
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 42]
Now the usual considerations apply :
- rebinding an arg has of course only local effect
- immutable objects are still immutables
Also note that since
1/ Python as a good support for exception handling
2/ a function can return multiple values [1],
there is less need for such constructs than in C or C++.
[1] the truth is that the function can return a unique tuple, that can
be unpacked as any other.
--
bruno desthuilliers
python -c print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in '[EMAIL PROTECTED]'.split('@')])
--
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Re: Bitching about the documentation...
Michael Spencer wrote: [...] Allowing quotation, almost anything is possible, e.g., Fred! Where Guido had had had, Had had had had had. Had had had a better effect on the reader or simply fred, where Guido had had had had had had had had had had, had a better effect on the reader M All this remind me about the Member of Parliament who was required to apologise for calling one of his opposite numbers a liar. He did so by reading out the statement I called the Honorable member a liar it is true and I am sorry for it, adding that the Honorable member could insert the punctuation wherever he so chose. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
Re: pyparsing with nested table
astarocean wrote:
using pyparsing to deal with nested tables , wanna keep table's
structure and propertys .
but program was chunked with the /td tag of inner table.
have any ideas?
here's the program
from pyparsing import *
... snip ...
tablePattern = Forward()
... snip ...
tablePattern = getMultiLevelPattern('table',trPattern)
t = tablePattern
for toks,strt,end in t.scanString(mytable):
print toks.asList()
Load Forward's with '' instead of '='. Change:
tablePattern = getMultiLevelPattern('table',trPattern)
to:
tablePattern getMultiLevelPattern('table',trPattern)
I think that is all you needed.
Awesome job! (Also check out the pyparsing built-ins for making HTML
and XML tags.)
-- Paul
--
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Re: what's wrong with lambda x : print x/60,x%60
Steven D'Aprano wrote: On Wed, 07 Dec 2005 10:59:09 +0100, Sybren Stuvel wrote: [...] But then you have all these small functions lying around in your module. If you intend to use them multiple times, then obviously you should keep them. But if they are intended to be used once, and once only, it seems bad to leave them there tempting fate. E.g. you have some code that uses a large lookup table. Rather than type the lookup table in by hand, you write a function which creates all or part of it. Once the lookup table is created, you shouldn't use that function again -- at best it is just sitting around like a third wheel, at worst it might have side-effects you don't want. So I del the function. The logic seems impeccable to me, and yet somehow deleting them after they are used feels ... not so much wrong, as just ... worthy of a head-scratching. In cases like this you would be like the law, and not concern yourself with trifles. In the majority of cases it costs you more to think about this and do the typing than it saves. I've no objection to the practice when it makes a difference, but ask yourself how many bytes you are saving by allowing the code for that function to be collected. Having said this, neither do I have any objection to your continuing to anally tidy up your namespace, but then I'm a slob whose partner is a neat freak, so I'm well used to accommodating the unnecessary. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
Re: sql escaping module
David Bear wrote: Being new to pgdb, I'm finding there are lot of things I don't understand when I read the PEP and the sparse documentation on pgdb. I was hoping there would be a module that would properly escape longer text strings to prevent sql injection -- and other things just make sure the python string object ends up being a properly type for postgresql. I've bought 3 books on postgresql and none of th code samples demonstrate this. web searchs for 'python sql escape string' yeild way too many results. Any pointers would be greatly appreciated. I think I know where David is coming from, as I also battled to understand this. I think that I have now 'got it', so I would like to offer my explanation. I used to think that each DB-API module transformed the 'string + parameters' into a valid SQL command before passing it to the db. However, this is not what is happening. Every modern database provides an API to allow applications to interact with the database programmatically. Typically these are intended for C programs, but other languages may be supported. The authors of the various DB-API modules provide a python wrapper around this to allow use from a python program. Each of the API's includes the capability of passing commands in the form of 'string + parameters' directly into the database. This means that the data values are never embedded into the SQL command at all, and therefore there is no possibility of injection attacks. The various API's use different syntaxes for passing the parameters. It would have been nice if the DB-API had specified one method, and left it to the author of each module to transform this into the form required by the underlying API. Unfortunately the DB-API allows a choice of 'paramstyles'. There may be technical reasons for this, but it does make supporting multiple databases awkward. Frank Millman -- http://mail.python.org/mailman/listinfo/python-list
Re: what's wrong with lambda x : print x/60,x%60
Paul Rubin wrote: Steve Holden [EMAIL PROTECTED] writes: All joking aside, when I have names (temporary variables or scaffolding functions) that I need to initialise a module or data structure, but then outlive their usefulness, I del the name afterwards. Am I the only one? I can't say I've seen anyone else doing that, and it feels icky to me (for no reason I can put my finger on) -- what do others think? I do that too sometimes. I think it's a Python weakness that you can't declare a local var like in other languages, to go out of scope at the end of the current block, e.g.: if cond: my x = 7# make a new scope for x, goes out of scope at end of if If this genuinely troubles you then you can always isolate the scope with a function, though of course you also no longer have the code inline then. I don't generally speaking see the point: unless the name is referencing something potentially large (like the results of a database query) and won't be going out of scope soon (which typically happens at the end of the current method or function) I just leave it to happen automatically. If it doesn't happen (because the name exists at module scope) thwn what the heck. Well, that makes the code a little bit confusing. If you say x = some_intermediate_result(...) do_something_with (x) do you know for sure whether x will be needed again? Yes. Are you sure you didn't use the name x further up in the function for something that's still needed? Yes. Of course, otherwise I wouldn't have used it here, would I? Meaningful names are the biggest help in avoiding errors like this. Are you trying to suggest my memory's going? ;-) This is one of the areas where there's tension between Python the scripting language, that gains by saving a few keystrokes when throwing together a quick hack, and Python the language for developing long-lasting applications that have to be maintained by multiple people. In Haskell you can even have temporary variables inside an expression: x = y + y*y + 3 where y=5 sets x to 33. I believe (not absolutely sure) that the scope of y is limited to that expression. Well, as warts go the inability to tightly control the scope of variables isn't really that terrible, is it? regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
Re: first post: new to pythong. some questions.
On 12/8/05, shawn a [EMAIL PROTECTED] wrote: Hello. Im brand new to this list and to python. Ive recently started reading about it and am now in the tinkering stage. Welcome to Python! I have a script im working on that i need some asistance debugging. Its super small and should be a snap for you gurus =) I have 2 files in a dir off my home dir: mkoneurl.py make_ou_class.py --mkoneurl.py-- #! /usr/bin/env python import make_ou_class run = makeoneurl() You need: run = make_ou_class.makeoneurl() See http://docs.python.org/tut/node8.html for why. (BTW, you would probably have got more of a response with a better subject line. http://www.catb.org/~esr/faqs/smart-questions.html is worth a read.) -- Cheers, Simon B, [EMAIL PROTECTED], http://www.brunningonline.net/simon/blog/ -- http://mail.python.org/mailman/listinfo/python-list
Re: sql escaping module
Frank Millman wrote: Each of the API's includes the capability of passing commands in the form of 'string + parameters' directly into the database. This means that the data values are never embedded into the SQL command at all, and therefore there is no possibility of injection attacks. another advantage with parameters is that if you do multiple operations which differ only in parameters, the database may skip the SQL compilation and query optimization passes. The various API's use different syntaxes for passing the parameters. It would have been nice if the DB-API had specified one method, and left it to the author of each module to transform this into the form required by the underlying API. Unfortunately the DB-API allows a choice of 'paramstyles'. There may be technical reasons for this, but it does make supporting multiple databases awkward. agreed. on the other hand, it shouldn't be that hard to create a function does this mapping on the fly, so that drivers can be updated support any paramstyle... time for a DB API 3.0 specification, perhaps ? (I'd also like to see a better granularity; the current connection/cursor model is a bit limited; a connection/cursor/query/result set model would be nicer, but I guess ODBC gets in the way here...) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Another newbie question
I think that's supposed to be [(i + j) % 2] for the index to the
(green,red) tuple
(since i*8 is always even).
[EMAIL PROTECTED] wrote:
Mike,
Thanks for your insight. It has been a big help.
I guess I was trying to learn too much with my original code. Trying to
implement inheritance, object creation, calling methods via inheritance
made the code harder than it needed to be.
I'm off to study the code. (Hmm.. how does python parse (green,
red)[(i * 8 + j) % 2] command ... he says while reaching for python
for the semi-illiterate ...)
Again, thanks for your help.
Jpl
Mike Meyer wrote:
solaris_1234 [EMAIL PROTECTED] writes:
1) The stmt board.Blist[10].DrawQueen(board.Blist[10].b1) seems
awkward. Is there another way (cleaner, more intuitive) to get the
same thing done?
Yes. Reaching through objects to do things is usually a bad idea. Some
languages don't allow you to do that at all; they require you to
provide methods for manipulating the state of the object For instance,
you can extend your MyBoard class with an extra method:
def DrawQueen(self, cell):
square = self.Blist[cell]
square.DrawQueen(square.b1)
And then those two lines become:
board.DrawQueen(10)
board.DrawQueen(22)
Except that's still ugly - you probably want something like
board.DrawQueen(1, 2).
Basically, Blist should be part of MyBoards implementation, not a
visible attribute. You should define methods for MyBoard that let
clients manipulate the board, without needing to know how it's
represented internally.
Along the same lines, why does MyBoard inherit from MyBox? It's not
using any of the features of MyBox. The code still works if you don't
do that. And why do you pass instances of Cavnas to the methods of
MyBox - it's got a canvas already! Do you really expect a MyBox to
draw onto Canvases other than it's own (if so, that's a bad design as
well).
Here's an updated version of your code. I've used the convention of an
_ prefix on attributes to indicate implementation details, and made
the classes inherit from object, as well as using box instead of
b1, and changed the interface to MyBoard squares to use standard
2d-array indexing instead of forcing the clients to do array
index calculations. You may have a good reason for doing these things
that doesn't appear in your code fragment, but I consider these to be
improvements in the fragment.
Hmm. b1 seems to indicate that you will eventually have more than
one canvas, which is why you passed in the canvas? In which case, the
distinguishing feature would be the number (or mabye the b1). In
that case, have your clients pass in the number (or name), and look up
the canvas in an internal structure.
mike
from Tkinter import *
import time
totalSolutionCount = 0
class MyBox(object):
def __init__(self, myC, myrow, mycolumn, color):
self._box = Canvas(myC, background=color, width=50, height=50)
self._box.grid(row=myrow, column=mycolumn)
self.occupied = False
def ChangebgColor(self):
self._box.config(bg=black)
def DrawQueen(self):
self._box.item = self._box.create_oval(4,4,50,50,fill=black)
self.occupied = True
self._box.update()
def unDrawQueen(self):
self._box.delete(self._box.item)
self.occupied = False
self._box.update()
class MyBoard(object) :
def __init__(self, myC):
self._blist = {}
for i in range(8):
for j in range(8):
self._blist[i, j] = MyBox(myContainer, i, j,
(green, red)[(i * 8 + j) % 2])
def DrawQueen(self, i, j):
square = self._blist[i, j]
square.DrawQueen()
def occupied(self, i, j):
return self._blist[i, j].occupied
root=Tk()
myContainer = Frame(root)
myContainer.pack()
board=MyBoard(myContainer)
board.DrawQueen(1, 2)
board.DrawQueen(2, 6)
raw_input() # A Hack debug statement
for i in range(8):
for j in range(8):
if board.occupied(i, j):
print %d, %d is occupied % (i, j)
raw_input() # A Hack debug statement
print \n*3
--
Mike Meyer [EMAIL PROTECTED]
http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more
information.
--
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Re: ElementTree - Why not part of the core?
[EMAIL PROTECTED] wrote: ElementTree on the other hand provides incredibly easy access to XML elements and works in a more Pythonic way. Why has the API not been included in the Python core? I'd really like to see that too. Sure, it's fairly trivial to install it, but each different package that needs to be installed from another source, built and tested on multiple platforms etc, means more work. For complex software systems, these kinds of configuration issues take a lot of efforts. We're deploying our software on a number of different platforms. We certainly depend on Python, so a standard Python install will always be included. Using standard library modules is for free. Using yet another third party library has a cost, even if some Cheese Shop or whatever might make the cost slightly lower. We have very friendly configuration management guys here, so if I insisted, I'm sure they'd let me have elementTree included, but I hesitate to ask for it. It does add a burden on CM, increases the risk that a deployment will fail, and from a code maintenance point of view, it's a double edged sword: On one hand, it's a much better API, but on the other hand, it's not documented in the standard Python docs or in the Nutshell book, and a new developer would need to figure out what this foreign beast was, and where to find docs. (Alternatively, I'd have to (God forbid) document my actions. ;) -- http://mail.python.org/mailman/listinfo/python-list
spawnle umask
Hi, I tried something like this but the umask part does not work clearly...: newpid = os.spawnle(os.P_NOWAIT,'/usr/bin/touch','/usr/bin/touch','xyz','umask 0113') What would be the correct syntax for setting the umask for the created process...? Best regards, Yves -- http://mail.python.org/mailman/listinfo/python-list
Re: Mutability of function arguments?
Mike Meyer wrote: ex_ottoyuhr [EMAIL PROTECTED] writes: I'm trying to create a function that can take arguments, say, foo and bar, and modify the original copies of foo and bar as well as its local versions -- the equivalent of C++ funct(foo, bar). C++'s '' causes an argument to be passed by reference. Python does that with all arguments. Any changes you make to the argument in the function will be seen in the caller unless you explicitly make a copy to pass. I would say, from the point of view of a C++ programmer, Python passes references by value. In other words if you think of variables as pointers (references) to values, and function call as passing the reference by value, the behaviour of Python makes sense. Kent -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie Q on sdtin word completion
Bernd wrote: I'm on a Linux env and try to get word completion form sdtin done, like Perl's $stdin = Complete( \t: , @choices ); What I have so far shows me the directory listing on the second hit on TAB and not the list of choices on the first like I wanted to have. your completer function is called with a prefix and an index. for each completion request, readline will call this function repeatedly, with in- creasing indices. for each call, you should return the corresponding match, or None if there are no more matches. the second example on this page might help: http://effbot.org/librarybook/readline.htm /F -- http://mail.python.org/mailman/listinfo/python-list
Re: spawnle umask
Yves Glodt wrote: I tried something like this but the umask part does not work clearly...: newpid = os.spawnle(os.P_NOWAIT,'/usr/bin/touch','/usr/bin/touch','xyz','umask 0113') What would be the correct syntax for setting the umask for the created process...? not sure, but something like try: old_mask = os.umask(0113) newpid = os.spawnle(...) finally: os.umask(old_mask) # restore might work. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: spawnle umask
Fredrik Lundh wrote: Yves Glodt wrote: I tried something like this but the umask part does not work clearly...: newpid = os.spawnle(os.P_NOWAIT,'/usr/bin/touch','/usr/bin/touch','xyz','umask 0113') What would be the correct syntax for setting the umask for the created process...? not sure, but something like try: old_mask = os.umask(0113) newpid = os.spawnle(...) finally: os.umask(old_mask) # restore might work. It does, I did like this: os.umask(0113) newpid = os.spawnl(os.P_NOWAIT,'/usr/local/bin/wine','/usr/local/bin/wine',executable) But I wanted to use spawnle and it's env argument, to avoid setting umask manually... regards, Yves /F -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
Magnus Lycka wrote: We're deploying our software on a number of different platforms. We certainly depend on Python, so a standard Python install will always be included. Using standard library modules is for free. Using yet another third party library has a cost, even if some Cheese Shop or whatever might make the cost slightly lower. We have very friendly configuration management guys here, so if I insisted, I'm sure they'd let me have elementTree included, but I hesitate to ask for it. It does add a burden on CM, increases the risk that a deployment will fail, and from a code maintenance point of view, it's a double edged sword: On one hand, it's a much better API, but on the other hand, it's not documented in the standard Python docs or in the Nutshell book, and a new developer would need to figure out what this foreign beast was, and where to find docs. (Alternatively, I'd have to (God forbid) document my actions. ;) on the other hand, you can bundle ElementTree with your applications simply by including the ElementTree.py and (optionally) the ElementPath.py modules. (you are allowed to add new Python modules to the project, I hope ;-) (and yes, HTML documentation is included in the source distribution kit) but seriously, given how easy it is to build things with distutils, I don't think your configuration folks would have much trouble adding support for anything that has a setup file, and is reasonably self-contained to their build scripts. we usually use one large shell script with a bunch of cd source; run setup install sections in it, e.g. cd $PREFIX cd src/griblib-2.1.1-20051125 $PYTHON setup.py install --prefix=$PREFIX plus a Python script that does a sanity check at the end to make sure that the build script actually managed to build and install everything we need. running the regression test suite on the build is a good way to weed out build problems too; just make sure you redirect the build output to a file, so you can check the logs afterwards. all source kits are checked into the version management system, of course. no tarballs are involved in the build process. just check things out and run the script, wait a couple of minutes, and you're done. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: sql escaping module
Fredrik Lundh wrote: Frank Millman wrote: Each of the API's includes the capability of passing commands in the form of 'string + parameters' directly into the database. This means that the data values are never embedded into the SQL command at all, and therefore there is no possibility of injection attacks. another advantage with parameters is that if you do multiple operations which differ only in parameters, the database may skip the SQL compilation and query optimization passes. The various API's use different syntaxes for passing the parameters. It would have been nice if the DB-API had specified one method, and left it to the author of each module to transform this into the form required by the underlying API. Unfortunately the DB-API allows a choice of 'paramstyles'. There may be technical reasons for this, but it does make supporting multiple databases awkward. agreed. indeed. I suspect (not having been involved in the decisions) that the variations were to minimise the work module implementers had to do to get their modules working. on the other hand, it shouldn't be that hard to create a function does this mapping on the fly, so that drivers can be updated support any paramstyle... time for a DB API 3.0 specification, perhaps ? It would be a little tricky to convert name-based (named and pyformat, requiring a data mapping) parameterizations to positional ones (qmark, numeric and format, requiring a data sequence) and vice versa. It's probably a worthwhile effort, though. (I'd also like to see a better granularity; the current connection/cursor model is a bit limited; a connection/cursor/query/result set model would be nicer, but I guess ODBC gets in the way here...) Yes, it would at least be nice to include some of the more advanced ways of presenting query results. regards Steve -- Steve Holden +44 150 684 7255 +1 800 494 3119 Holden Web LLC www.holdenweb.com PyCon TX 2006 www.python.org/pycon/ -- http://mail.python.org/mailman/listinfo/python-list
How to get the extension of a filename from the path
Hello, what is a way to get the the extension of a filename from the path? E.g., on my XP windows the path can be C:\Pictures\MyDocs\test.txt and I would like to get the the extension of the filename, that is here txt I would like that to work on Linux also Thank you for help L. -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
Fredrik Lundh wrote: Steven Bethard wrote: ElementTree on the other hand provides incredibly easy access to XML elements and works in a more Pythonic way. Why has the API not been included in the Python core? While I fully agree that ElementTree is far more Pythonic than the dom-based stuff in the core, this issue has been discussed on python-dev[1]. Fredrik Lundh's response: shipping stable versions of ElementTree/cElementTree (or PIL, or python-doc, or exemaker, or what else you might find useful) with official Python releases is perfectly okay. moving the main trunk and main development over to the Python CVS is another thing, entirely. I think some people were hoping that instead of adding these things to the standard library, we would come up with a better package manager that would make adding these things to your local library much simpler. I still hope that the standard distribution will, in a not too distant future, bundle more external libraries. as things are today, including something in the core means that you have to transfer code and rights to the PSF. as I've said many times, if the Linux folks can build distributions that con- sists of thousands of individually maintained pieces, the Python distributors should be able to handle a few dozen components. I'd like to add my vote in favour of this. There are a few popular extensions that most users would like easy access to. PIL and ElementTree both fall into this category. Thanks Fuzzyman http://www.voidspace.org.uk/python/index.shtml /F -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
Lad wrote:
Hello,
what is a way to get the the extension of a filename from the path?
E.g., on my XP windows the path can be
C:\Pictures\MyDocs\test.txt
and I would like to get
the the extension of the filename, that is here
txt
I would like that to work on Linux also
Thank you for help
L.
Like this, you mean?
import os.path
os.path.splitext(c:\\pictures\\mydocs\\test.txt)
('c:\\pictures\\mydocs\\test', '.txt')
--
Dale Strickland-Clark
Riverhall Systems www.riverhall.co.uk
--
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Re: ElementTree - Why not part of the core?
[EMAIL PROTECTED] wrote: I think some people were hoping that instead of adding these things to the standard library, we would come up with a better package manager that would make adding these things to your local library much simpler. STeVe [1]http://www.python.org/dev/summary/2005-06-01_2005-06-15.html#reorganising-th e-standard-library-again A better package manager would be great but does not replace having things in the core. Distributed code that relies on external packages puts a significantly greater burden on the user of the code. Seconded. One thing I really fear about the otherwise great EasyInstall (and Python Eggs) is that we could forget about Let's not turn the Python standard library into the CPAN mess, where there are 5 different libraries for adding two numbers, so that it's then impossible to grab a random perl program and read it, without going through 150 different man pages you never saw before. I don't need 450 libraries to compute MD5, or to zip a file, or 140 different implementations of random numbers. There will always be external libraries for specific purposes, but I'd rather the standard library to stay focused on provided a possibly restricted set of common features with a decent interface/implementation. This said, I'd also like to see ElementTree in the standard library. We already have a SAX and a DOM, but we need a Pythonic XML library, and ElementTree is just perfect. -- Giovanni Bajo -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
On Thu, 8 Dec 2005, Lad wrote:
what is a way to get the the extension of a filename from the path?
E.g., on my XP windows the path can be
C:\Pictures\MyDocs\test.txt
and I would like to get
the the extension of the filename, that is here
txt
You want os.path.splitext:
import os
os.path.splitext(C:\Pictures\MyDocs\test.txt)
('C:\\Pictures\\MyDocs\test', '.txt')
os.path.splitext(C:\Pictures\MyDocs\test.txt)[1]
'.txt'
I would like that to work on Linux also
It'll be fine.
tom
--
[Philosophy] is kind of like being driven behind the sofa by Dr Who -
scary, but still entertaining. -- Itchyfidget
--
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Re: ElementTree - Why not part of the core?
Giovanni Bajo wrote: One thing I really fear about the otherwise great EasyInstall (and Python Eggs) is that we could forget about... ... how important is to have a standard library. The fact that it's easy to install external modules shouldn't make us drop the standard library. A standard library means a great uniformity across programs. Whenever I open a Python program which uses ZipFile, or socket, or re, I can read it *immediately*. If it uses an external library / framework, I have to go study its manual and documentation. Proliferation of external libraries is good, but people should normally use the standard library modules for uniformity. In other words, I disagree with this message: http://mail.python.org/pipermail/python-dev/2005-June/054102.html My personal hope is that Python 3.0 will have a nice cleaned-up standard library with even more features than Python 2.x. As I said the in other message, let's not end up into the CPAN mess just because it's now technically easier! -- Giovanni Bajo -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
Lad [EMAIL PROTECTED] wrote: what is a way to get the the extension of a filename from the path? E.g., on my XP windows the path can be C:\Pictures\MyDocs\test.txt and I would like to get the the extension of the filename, that is here txt I would like that to work on Linux also Thank you for help os.path.splitext(filename) splits a filename into a name part (which may include a path) and an extension part: import os f, e = os.path.splitext(filename) the extension will include the separator, so the following is always true: assert f + e == filename if you don't want the period, you can strip it off: if e[:1] == .: e = e[1:] but it's often easier to change your code to take the dot into account; instead of if e[:1] == .: e = e[1:] if e == txt: handle_text_file(filename) elif e in (png, jpg): handle_image_file(filename) do if e == .txt: handle_text_file(filename) elif e in (.png, .jpg): handle_image_file(filename) on the other hand, for maximum portability, you can use f, e = os.path.splitext(filename) if e.startswith(os.extsep): e = e[len(os.extsep):] if e == txt: ... but that's probably overkill... /F -- http://mail.python.org/mailman/listinfo/python-list
Re: pyparsing with nested table
Paul McGuire wrote:
Load Forward's with '' instead of '='. Change:
tablePattern = getMultiLevelPattern('table',trPattern)
to:
tablePattern getMultiLevelPattern('table',trPattern)
I think that is all you needed.
Awesome job! (Also check out the pyparsing built-ins for making HTML
and XML tags.)
-- Paul
thank you , i was wonding why my iteraiton not functional . so it's my
fault .
later , i checked other parsers like Clientable BeautifulSoap ,
i think with beautifulsoap doing this job is a better idea.
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Re: How to get the extension of a filename from the path
Lad wrote: Hello, what is a way to get the the extension of a filename from the path? E.g., on my XP windows the path can be C:\Pictures\MyDocs\test.txt and I would like to get the the extension of the filename, that is here txt I would like that to work on Linux also Thank you for help L. minor footnote: windows paths can be raw strings for os.path.split(), or you can escape / tho Tom's examp indicates unescaped, non-raw string works with splitext() import os.path # winpath='C:\\Pictures\\MyDocs\\test.txt' winpath=r'C:\Pictures\MyDocs\test.txt' fpath,fname_ext=os.path.split(winpath) print path: %s ; fname and ext: %s%(fpath, fname_ext) ext=fname_ext.split(.)[-1] print ext -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
Fredrik Lundh wrote: but seriously, given how easy it is to build things with distutils, I don't think your configuration folks would have much trouble adding support for anything that has a setup file, and is reasonably self-contained to their build scripts. True. It's one more thing to keep track of though. It's a separate configuration item. We need to keep track of which version to use, and it needs to get built, installed and validated on all supported platforms. I already include Twisted (and thus ZopeInterface) like that. We sometimes need high speed in XML parsing, so I'd like to use cElementTree, but just like the two other packages, I assume that it's unproblematic to build the included C code. So, you're right, it's not much trouble, just two more pebbles (cElementTree and ElementTree) on a fairly heavy load, where stuff like Oracle and MQ Series are more like boulders. Right now, I would like to improve the performace of a program that does a lot of XML parsing. I haven't profiled that yet, so I don't know if XML parsing is the bottle neck, but if I can improve perfor- mance significantly with cElementTree, I'll certainly push for that. /Magnus -- http://mail.python.org/mailman/listinfo/python-list
Encoding of file names
Here is my situation: I am trying to programatically access files created on an IBM AIX system, stored on a Sun OS 5.8 fileserver, through a samba-mapped drive on a Win32 system. Not confused? OK, let's move on... ;-) When I ask for an os.listdir() of a relevant directory, I get filenames with embedded escaped characters (ex. 'F07JS41C.04389525AA.UPR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model') which will read as False when applying an os.path.isfile() to it. I wish to apply some operations to these files, but am unable, since python (on Win32, at least) does not recognize this as a valid filename. Help me, before my thin veneer of genius is torn from my boss's eyes! ;-) -- http://mail.python.org/mailman/listinfo/python-list
Re: spawnle umask
Yves Glodt wrote: It does, I did like this: os.umask(0113) newpid = os.spawnl(os.P_NOWAIT,'/usr/local/bin/wine','/usr/local/bin/wine',executable) But I wanted to use spawnle and it's env argument, to avoid setting umask manually... The umask is not part of the environment, so there's no way to set it directly through spawnle. Why don't you want to use os.umask? -- David -- http://mail.python.org/mailman/listinfo/python-list
Re: Python and OLAP?
Wolfgang Keller wrote: Hello, does anyone know of Python modules for OLAP work? E.g. efficient manipulation of large multi-dimensional structures (arrays) of arbitrary (not only numeric) data? TIA, Sincerely, Wolfgang Keller Perhaps this might be useful: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/334695 -- Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: efficient 'tail' implementation
[EMAIL PROTECTED] writes: hi I have a file which is very large eg over 200Mb , and i am going to use python to code a tail command to get the last few lines of the file. What is a good algorithm for this type of task in python for very big files? Initially, i thought of reading everything into an array from the file and just get the last few elements (lines) but since it's a very big file, don't think is efficient. thanks First of all, what makes you think that tail on your system isn't already optinized for this? Devil's advocate here... I have no clue really. Anyway, if you must roll your own; Determine some reasonable max line size,, multiply this by a few larger than the numbers of lines that you want to tail, seek to EOF and then back to the position in the file where this chunk would start, get and split that chunk into lines and now output the last 3 or however many you need. If the read fails to hold enough lines, seek back a bit further and do same but you'll have to be prepared to concat the second and Nth last chunks together. Have fun -- --- Jerry Sievers 305 854-3001 (home) WWW ECommerce Consultant 305 321-1144 (mobilehttp://www.JerrySievers.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
On 7 Dec 2005 05:51:45 -0800, Iain King [EMAIL PROTECTED] wrote: Argh, you made me look at the html again - at least now I know *why* it is so disgusting. I understand there's a new version coming out soon, hopefully in html 4 strict or xhtml. I'm sure at that point it'll be easier to use. I can wait. :) A new version of LaTeX2HTML, you mean? Can you provide a pointer? --amk -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
ElementTree on the other hand provides incredibly easy access to XML elements and works in a more Pythonic way. Why has the API not been included in the Python core? Magnus I'd really like to see that too. Sure, it's fairly trivial to Magnus install it, but each different package that needs to be Magnus installed from another source, built and tested on multiple Magnus platforms etc, means more work. More work than reimplementing the functionality or living with a miserable API (I'm thinking normal DOM APIs)? Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
ElementTree on the other hand provides incredibly easy access to XML elements and works in a more Pythonic way. Why has the API not been included in the Python core? I think the key here is ElementTree's Pythoninc API. While it's clearly possible to install it as a third-party package, I think there's a clear best-of-breed aspect here that suggests it belongs in the standard distribution simply to discourage continued use of DOM-based APIs. Skip -- http://mail.python.org/mailman/listinfo/python-list
Re: Python web publishing framework like Cocoon?
Dan M wrote: Dennis Benzinger wrote: Is there a Python web publishing framework like Cocoon? How about: [List of the usual suspects] just to name a few of my favorites. Take a look at http://wiki.python.org/moin/WebProgramming for a more complete list. Although it is good advice to recommend the WebProgramming page, despite my reservations about its current state, I don't think it is particularly helpful for everyone to shout out their favourites - as appears to be the normal practice on this topic - especially when none of the suggestions seem to share very much architecturally or technologically with Cocoon. Aside from Maki, which the questioner mentioned, I'd imagine that 4Suite Server [1] might have some overlap with Cocoon, although I've never managed to motivate myself past the introductions/installations and actually experiment with it. I can certainly admit that I've developed a forms toolkit [2] which makes use of XSLT, although you won't see in it anything like the XML-based site map configuration from Cocoon, and whilst I suppose you could implement such things on top of my toolkit, you'll need to spend some time replicating some of the other conveniences of Cocoon that it seems to manage all by itself (or at least after judicious editing of various lengthy configuration files). If the forms aspects of my toolkit aren't interesting, you could concentrate on just using stylesheets, although I will also admit that you could integrate convenient stylesheet processing with just about any Web framework, and there may be components out there which do just that. My experiences with Cocoon suggested that although the site map concept is rather enticing, one frequently needs to break out of the functional programming model that it enforces in order to provide more than very simple application logic, and I wasn't really encouraged by the Cocoon developers chosen means of doing this (server side JavaScript), nor by their ability to break functionality between microreleases. If you're happy transferring the site map logic into Python - not a difficult task - then you just need to choose a Web framework that doesn't fight you over how you do things like URL dispatching. Anyway, if you're interested in using XSLT with Python, speak up or get in touch. I think it's an area which has been unfairly overshadowed by more fashionable technologies. Paul [1] http://www.4suite.org/index.xhtml [2] http://www.python.org/pypi/XSLTools -- http://mail.python.org/mailman/listinfo/python-list
Dr. Dobb's Python-URL! - weekly Python news and links (Dec 7)
QOTW: ... and to my utter surprise it worked. - Andrew Nagel on his move from wxPython to programming Tkinter in desperation Python has more web application frameworks than keywords. - Skip Montanaro (but probably others going back years) Frithiof Andreas Jensen writes frankly on use of SNMP and netconf: http://groups.google.com/group/comp.lang.python/msg/662032bf92670fd7 Perhaps your application needs something like ping. Several distinct ways to achieve that exist: http://groups.google.com/group/comp.lang.python/browse_thread/thread/ced60d60b5942f1f/ You're going to hear about reddit.com, and about how it's been REimplemented in Python. Here's a fraction of the commentary: http://reddit.com/blog/2005/12/night-of-living-python.html http://www.aaronsw.com/weblog/rewritingreddit Long discussions about Python documentation lead to no conclusion this commentator knows how to summarize: http://groups.google.com/group/comp.lang.python/browse_thread/thread/767470cb3cbc24d5/ http://groups.google.com/group/comp.lang.python/browse_thread/thread/94e2e5244a90a274/ aum's pygene genetic-algorithm solver includes full api documentation, and an implementation of the travelling salesman problem ...: http://groups.google.com/group/comp.lang.python/browse_thread/thread/9901fe0f886893d6/ Jibes against the lambda-clingers lead eventually to serious questions of style in regard to variable namespacing, lifespan, cleanup, and so on: http://groups.google.com/group/comp.lang.python/browse_thread/thread/ad0e15cb6b8f2c32/ To say anything useful about IDEs apart from that one needs to try each on for personal fit seems *very* difficult: http://groups.google.com/group/comp.lang.python/browse_thread/thread/eca26b6e6617a591/ Everything Python-related you want is probably one or two clicks away in these pages: Python.org's Python Language Website is the traditional center of Pythonia http://www.python.org Notice especially the master FAQ http://www.python.org/doc/FAQ.html PythonWare complements the digest you're reading with the marvelous daily python url http://www.pythonware.com/daily Mygale is a news-gathering webcrawler that specializes in (new) World-Wide Web articles related to Python. http://www.awaretek.com/nowak/mygale.html While cosmetically similar, Mygale and the Daily Python-URL are utterly different in their technologies and generally in their results. For far, FAR more Python reading than any one mind should absorb, much of it quite interesting, several pages index much of the universe of Pybloggers. http://lowlife.jp/cgi-bin/moin.cgi/PythonProgrammersWeblog http://www.planetpython.org/ http://mechanicalcat.net/pyblagg.html comp.lang.python.announce announces new Python software. Be sure to scan this newsgroup weekly. http://groups.google.com/groups?oi=djqas_ugroup=comp.lang.python.announce Steve Bethard, Tim Lesher, and Tony Meyer continue the marvelous tradition early borne by Andrew Kuchling, Michael Hudson and Brett Cannon of intelligently summarizing action on the python-dev mailing list once every other week. http://www.python.org/dev/summary/ The Python Package Index catalogues packages. http://www.python.org/pypi/ The somewhat older Vaults of Parnassus ambitiously collects references to all sorts of Python resources. http://www.vex.net/~x/parnassus/ Much of Python's real work takes place on Special-Interest Group mailing lists http://www.python.org/sigs/ Python Success Stories--from air-traffic control to on-line match-making--can inspire you or decision-makers to whom you're subject with a vision of what the language makes practical. http://www.pythonology.com/success The Python Software Foundation (PSF) has replaced the Python Consortium as an independent nexus of activity. It has official responsibility for Python's development and maintenance. http://www.python.org/psf/ Among the ways you can support PSF is with a donation. http://www.python.org/psf/donate.html Kurt B. Kaiser publishes a weekly report on faults and patches. http://www.google.com/groups?as_usubject=weekly%20python%20patch Cetus collects Python hyperlinks. http://www.cetus-links.org/oo_python.html Python FAQTS http://python.faqts.com/ The Cookbook is a collaborative effort to capture useful and interesting recipes. http://aspn.activestate.com/ASPN/Cookbook/Python Among several Python-oriented RSS/RDF feeds available are http://www.python.org/channews.rdf
Re: spawnle umask
David Wahler wrote: Yves Glodt wrote: It does, I did like this: os.umask(0113) newpid = os.spawnl(os.P_NOWAIT,'/usr/local/bin/wine','/usr/local/bin/wine',executable) But I wanted to use spawnle and it's env argument, to avoid setting umask manually... The umask is not part of the environment, so there's no way to set it directly through spawnle. ok Why don't you want to use os.umask? Only because I thought spawnle could set it through env... But as it can't I will now go with os.umask. thanks, Yves -- David -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie Q on sdtin word completion
Thanks, exactly what I was looking for. I should go and buy you book ;-) Bernd Fredrik Lundh wrote: Bernd wrote: I'm on a Linux env and try to get word completion form sdtin done, like Perl's $stdin = Complete( \t: , @choices ); What I have so far shows me the directory listing on the second hit on TAB and not the list of choices on the first like I wanted to have. your completer function is called with a prefix and an index. for each completion request, readline will call this function repeatedly, with in- creasing indices. for each call, you should return the corresponding match, or None if there are no more matches. the second example on this page might help: http://effbot.org/librarybook/readline.htm /F -- http://mail.python.org/mailman/listinfo/python-list
Re: How do you create a custom QCursor in Python Qt?
Thanks Phil, Good idea, I had failed to notice these code examples and been struggling the qt3 examples from pyqtsrc.tgz for months. So, I found my mistake, I was using a 8*8 bitmap, I have now corrected it and use a 16*16 bitmap (which is the standard size on Mac OS X) read in from a PNG file created in Photoshop in bitmap mode and it works just great. I failed to read the C++ documentation for Qt closely enough where it states: Valid cursor sizes depend on the display hardware (or the underlying window system). We recommend using 32x32 cursors, because this size is supported on all platforms. Some platforms also support 16x16, 48x48 and 64x64 cursors. As a Python novice I had simply taken the bitmap that was available in the documentation for Qbitmap, which happens to be an 8*8 bitmap. Interestingly on my G5 iMac Mac OS X 10.4.3 running Python 2.4.1 Qt3.3.5 QCursors of both 16*16 32*32 works perfectly; whereas on my G4 Powerbook Mac OS X 10.4.2 running the same Python 2.4.1 Qt3.3.5, a 16*16 QCursor works but a 32*32 QCursor doesn't, but since there are no error messages that is all that I can report. Interesting! I have also tested my code on a PC, which supports 32*32 but does not support 16*16. --- I have two auxiliary questions if anybody can help me. 1: When I click on a button the cursor does not change immediately, the cursor only actually gets re-drawn when I physically move the mouse. Is there a way to get it to update instantaneously? After setCursor() I call repaint(True) but this does not have the desired effect. def bitmap(self): self.setCursor(self.inlineBitmapCursor) self.repaint(True) 2: The cursor that I want to customise is the wait cursor; under Mac OS X this is an animated cursor displaying a wristwatch with hands that go around? So my question is where do I find the code that produces this effect, is it written in C++ or Python and how can I imitate it? Steve -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
Fredrik Lundh wrote: on the other hand, for maximum portability, you can use f, e = os.path.splitext(filename) if e.startswith(os.extsep): e = e[len(os.extsep):] if e == txt: ... Is there ever a time when the original `e` could evaluate True, yet not startswith(os.extsep)? In other words, could the first test be just if e: e = e[len(os.extsep):] Also, note that for truly maximum portability one probably needs to add to the code some knowledge of case-sensitivity and do a .lower() when appropriate, as txt and TXT (and others) are equivalent on Windows file systems. On that note, is there a common idiom for detecting that information? -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Encoding of file names
utabintarbo wrote: I am trying to programatically access files created on an IBM AIX system, stored on a Sun OS 5.8 fileserver, through a samba-mapped drive on a Win32 system. Not confused? OK, let's move on... ;-) When I ask for an os.listdir() of a relevant directory, I get filenames with embedded escaped characters (ex. 'F07JS41C.04389525AA.UPR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model') which will read as False when applying an os.path.isfile() to it. I wish to apply some operations to these files, but am unable, since python (on Win32, at least) does not recognize this as a valid filename. I'm not sure of the answer, but note that .isfile() is not just checking whether the filename is valid, it's checking that something *exists* with that name, and that it is a file. Big difference... at least in telling you where to look for the solution. In this case, checking which of the two tests in ntpath.isfile() is actually failing might be a first step if you don't have some other lead. (ntpath is what os.path translates into on Windows, so look for ntpath.py in the Python lib folder.) If you're really seeing what you're seeing, I suspect a bug since if os.listdir() can find it (and it's really a file), os.isfile() should report it as a file, I would think. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: efficient 'tail' implementation
Gerald Klix [EMAIL PROTECTED] wrote: As long as memory mapped files are available, the fastest method is to map the whole file into memory and use the mappings rfind method to search for an end of line. Excellent idea. It'll blow up for large 2GB files on a 32bit OS though. -- Nick Craig-Wood [EMAIL PROTECTED] -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
On Wed, 07 Dec 2005 12:10:18 -0500, Kent Johnson [EMAIL PROTECTED] wrote: OK I'll bite. That Beginners Guide page has bugged me for a long time. It's a wiki page but it is marked as immutable so I can't change it. Here are some immediate suggestions: Good suggestions; thanks! I've applied most of them. - Change the sentence Read BeginnersGuide/Overview to learn the key points. to Read BeginnersGuide/Overview to learn what makes Python special. Or maybe get rid of it completely - I'm not sure evangelism belongs on this page. Yes, it does; fairly often the webmaster alias receives e-mails that ask so what is Python? --amk -- http://mail.python.org/mailman/listinfo/python-list
Is there anything that pickle + copy_reg cannot serialize?
Hi, I need to look into serialization for python objects, including codes, recursive types etc etc. Currently, I have no idea exactly what needs to be serialized, so my scope is to be as wide as possible. I understand that marshal is extended by pickle to serialize class instances, shared elements, and recursive data structures (http://www.effbot.org/librarybook/pickle.htm) but cannot handle code types. pickle can be used together with copy_reg and marshal to serialize code types as well (http://www.effbot.org/librarybook/copy-reg.htm). So my question will be, are there anything that pickle/copy_reg/marshal combination cannot serialize? If so, what are the workarounds? Thanks Maurice -- http://mail.python.org/mailman/listinfo/python-list
Re: ANN: Dao Language v.0.9.6-beta is release!
On 8 Dec 2005 08:17:14 GMT in comp.lang.python, Antoon Pardon [EMAIL PROTECTED] wrote: [...] I just think braces are the worst solution for it, as python is concerned. Agreed. A model like Modula-2's would be much preferable, and in fact is supported (but not enforced) today (as long as you also obey indentation rules). Just mark the end of your blocks with #endif, #endfor, #endwhile, #enddef, #endclass, #endwhatever as appropriate. Regards, -=Dave -- Change is inevitable, progress is not. -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
I still hope that the standard distribution will, in a not too distant future, bundle more external libraries. as things are today, including something in the core means that you have to transfer code and rights to the PSF. Your description of how to include something in the core isn't entirely accurate. If you visit http://www.python.org/psf/contrib.html, you'll see that you don't need to transfer your rights to the PSF. Rather, you need to sign an agreement giving the PSF the rights to relicense the code. The PSF currently require that the original submission be licensed under one of two open source licenses. Personally, I can imagine accepting a wider range of initial licenses in the future. As for transferring the code, there needs to be a copy in the Python source control system, sure. There's some unavoidable complexity involved in managing a software distribution composed of third party software packages. At the very least, you've got the original sources and the copy in the distribution package, which leads to a synchronization problem. Jeremy -- http://mail.python.org/mailman/listinfo/python-list
Re: Mutability of function arguments?
Kent Johnson [EMAIL PROTECTED] writes: Mike Meyer wrote: ex_ottoyuhr [EMAIL PROTECTED] writes: I'm trying to create a function that can take arguments, say, foo and bar, and modify the original copies of foo and bar as well as its local versions -- the equivalent of C++ funct(foo, bar). C++'s '' causes an argument to be passed by reference. Python does that with all arguments. Any changes you make to the argument in the function will be seen in the caller unless you explicitly make a copy to pass. I would say, from the point of view of a C++ programmer, Python passes references by value. In other words if you think of variables as pointers (references) to values, and function call as passing the reference by value, the behaviour of Python makes sense. While the description is right, the terminology is wrong, and places the emphasis in the wrong place. Your description of passes references by value is a description of call by reference. C passes all arguments by value, to pass a reference, the C programmer creates the reference to the value by hand, then dereferences it by hand at the other end. So C's call-by-reference passes the reference by value. There's no difference between C's call-by-reference and Python's call-by-reference, and using different words to try and imply there is will just cause problems further on. The real difference is in the way names behave in the two languages. As you put it, variables are references to values, except Python names don't have most of the things associated with variables in other programming languages, so it's better to call them names. We use bound to show that we're not copying a value over a fixed memory location, hence names are bound to values. This is the crucial point, and the one that need to be emphasized. mike -- Mike Meyer [EMAIL PROTECTED] http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
Thank you ALL for help Regards, L. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitching about the documentation...
Fredrik Lundh wrote: Rocco Moretti wrote: Insert punctuation capitalization to make the following a correct and coherent (if not a little tourtured). fred where guido had had had had had had had had had had had a better effect on the reader punctuation, including quote marks, I presume? Quote marks are acceptable, but no more than two words are inside each set. B A D G E R . . . E R S P O I L E R W A R N I N G The accepted way to do it is: Fred, where Guido had had had, had had had had. Had had had had a better effect on the reader. meaning approximately In the place where Guido previously put the word had, Fred had previously put the phrase had had. Fred's choice of phrasing was more appreciated by the reder. -- http://mail.python.org/mailman/listinfo/python-list
Re: Encoding of file names
utabintarbo wrote: I am trying to programatically access files created on an IBM AIX system, stored on a Sun OS 5.8 fileserver, through a samba-mapped drive on a Win32 system. Not confused? OK, let's move on... ;-) When I ask for an os.listdir() of a relevant directory, I get filenames with embedded escaped characters (ex. 'F07JS41C.04389525AA.UPR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model') which will read as False when applying an os.path.isfile() to it. I wish to apply some operations to these files, but am unable, since python (on Win32, at least) does not recognize this as a valid filename. Does the problem persist if you feed os.listdir() a unicode path? This will cause listdir() to return unicode filenames which are less prone to encoding confusion. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: efficient 'tail' implementation
Gerald Klix [EMAIL PROTECTED] wrote: As long as memory mapped files are available, the fastest method is to map the whole file into memory and use the mappings rfind method to search for an end of line. Actually mmap doesn't appear to have an rfind method :-( Here is a tested solution using mmap using your code. Inefficient if number of lines to be tailed is too big. import os import sys import mmap def main(nlines, filename): reportFile = open( filename ) length = os.fstat( reportFile.fileno() ).st_size if length == 0: # Don't map zero length files, windows will barf return try: mapping = mmap.mmap( reportFile.fileno(), length, mmap.MAP_PRIVATE, mmap.PROT_READ ) except AttributeError: mapping = mmap.mmap( reportFile.fileno(), 0, None, mmap.ACCESS_READ ) search = 1024 lines = [] while 1: if search length: search = length tail = mapping[length-search:] lines = tail.split(os.linesep) if len(lines) = nlines or search == length: break search *= 2 lines = lines[-nlines-1:] print \n.join(lines) if __name__ == __main__: if len(sys.argv) != 3: print Syntax: %s n file % sys.argv[0] else: main(int(sys.argv[1]), sys.argv[2]) -- Nick Craig-Wood [EMAIL PROTECTED] -- http://www.craig-wood.com/nick -- http://mail.python.org/mailman/listinfo/python-list
Post-modernism, Academia, and the Tech Geeking fuckheads
Post-modernism, Academia, and the Tech Geeking fuckheads • the Sokal Affair http://en.wikipedia.org/wiki/Sokal_Affair • SCIGen and World Multi-Conference on Systemics, Cybernetics and Informatics http://pdos.csail.mit.edu/scigen/ • What are OOP's Jargons and Complexities, Xah Lee http://xahlee.org/Periodic_dosage_dir/t2/oop.html • Politics and the English Language, George Orwell http://xahlee.org/p/george_orwell_english.html Xah [EMAIL PROTECTED] ∑ http://xahlee.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Encoding of file names
utabintarbo wrote: Here is my situation: I am trying to programatically access files created on an IBM AIX system, stored on a Sun OS 5.8 fileserver, through a samba-mapped drive on a Win32 system. Not confused? OK, let's move on... ;-) When I ask for an os.listdir() of a relevant directory, I get filenames with embedded escaped characters (ex. 'F07JS41C.04389525AA.UPR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model') which will read as False when applying an os.path.isfile() to it. I wish to apply some operations to these files, but am unable, since python (on Win32, at least) does not recognize this as a valid filename. Just to eliminate the obvious, you are calling os.path.join() with the parent name before calling isfile(), yes? Something like for f in os.listdir(someDir): fp = os.path.join(someDir, f) if os.path.isfile(fp): ... Kent -- http://mail.python.org/mailman/listinfo/python-list
Re: JPEG decoder not available in PIL
On 6 Dec 2005 14:02:37 -0800, Peter wrote: I have a problem which seems to come up from time to time but I can't find anything relevant in the archives. I have used PIL v1.1.5 with no problem on Windows for some time but now wish to put it on Linux (Suse Linux v10.0). I obtained and built the JPEG libraries (jpeg-6b) without any problem. The tests for the installation work fine. I built Python 2.4.2 from the sources but with no special options, just 'out of the box'. This works fine. PIL built as it should but the selftest.py fails with the 'decoder jpeg is not available' message (the other 54 tests are OK). Other images are opened and shown with xv, no problem. I think that there is something wrong with the libraries or the way they linked. It seems you did not build the RPMs for the JPEG libraries, so the include files were not placed in the correct location: # rpm -ql libjpeg-devel ... /usr/include/jpeglib.h ... Perhaps you should try yum install libjpeg libjpeg-devel if Suse supports yum. -Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
On Wed, 07 Dec 2005 12:58:36 -0800,
Michael Spencer [EMAIL PROTECTED] wrote:
I experimented with some more re-organization, but I don't see away
to attach the resulting file in the SF comments, so I'll post it
here instead.
I've attached your file to the patch. Some comments:
\input{libstruct} % also/better in File Formats?
Struct operates on string input and produces string output, so I think
it belongs in the string chapter where you've placed it. We need to
add more cross-references, so File Formats should mention struct as a
related module.
% Functions, Functional, Generators and Iterators
\input{libitertools}
\input{libfunctional}
\input{liboperator} % from runtime - better with itertools and
functional
% encoding stuff
...
\input{libxdrlib}
XDR is really more similar to struct or marshal, I think, but on the
other hand it is an Internet RFC (#1014). Not sure where it should go...
\input{libsomeos} % Optional Operating System Services
\input{libselect}
\input{libthread}
\input{libthreading}
\input{libdummythread}
\input{libdummythreading}
\input{libmmap}
\input{libreadline}
\input{librlcompleter}
\input{libunix} % UNIX Specific Services
\input{libposix}
\input{libpwd}
\input{libspwd}
\input{libgrp}
\input{libcrypt}
\input{libdl}
\input{libtermios}
\input{libtty}
\input{libpty}
\input{libfcntl}
\input{libpipes}
\input{libposixfile}
\input{libresource}
\input{libnis}
\input{libsyslog}
\input{libcommands}
\input{internet}% Internet Protocols
I wonder if the Internet chapter should be split into HTTP/Web Tools
(webbrowser, cgi, cgitb, httplib, urllib) and Non-Web Protocols
(ftplib, gopherlib, smtp, all the rest).
\input{distutils}
Distutils should probably be in Program Frameworks. Or it could just
have a chapter of its own, or maybe there are enough modules for an
Application Support chapter.
--amk
--
http://mail.python.org/mailman/listinfo/python-list
Re: Bitching about the documentation...
On Wed, 07 Dec 2005 12:33:07 -0600 in comp.lang.python, Rocco Moretti [EMAIL PROTECTED] wrote: [...] fred where guido had had had had had had had had had had had a better effect on the reader I've seen this before as bill had had had but will had had had had had had or had had been correct had had had Regards, -=Dave -- Change is inevitable, progress is not. -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
Andrew, The site changes for the new-to-Python person are a big improvement in terms of the sequence of exposures, but from a marketing perspective, the first thing they read about Python is still aimed at a programmer. The bulleted points in BeginnersGuide/Overview are, again, things that are important to programmers (Automatic garbage collection frees you from the hassles of memory management means nothing to me, even now after reading a Python book and several tutorials). I wish there were some sort of sexy exposure to Python before hitting them with the download. Again you purport to be making a page for someone who's never programmed before, so almost certainly a Windows user. And a Windows user is not going to download any program until he's absolutely sure it won't destabilize his fragile system or infect it. So nobody new to programming and new to Python is going to download at the point you present them with that opportunity. Too bad there isn't something like what Ruby does with the Try Ruby In Your Browser thing, which is a very effective marketing tool (although obviously I chose Python). http://tryruby.hobix.com/ The other thing I vividly recall struggling with was: Do I download this Python.org version for my Windows XP machine, because it's the official one, or do I use the one from ActiveState because others say it comes with all sorts of goodies for Windows users? I don't know what the politics are there, but if I were you I'd take a stand and put it on the download page to help the new person out, who is uncertain about what to do. Ultimately I downloaded ActiveState because I found their site easier to understand (again speaking as a person relatively new to programming and absolutely new to Python). Thanks, rpd I read part of it all the way through.--Samuel Goldwyn www.dooling.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
A.M. Kuchling wrote: On Wed, 07 Dec 2005 12:10:18 -0500, Kent Johnson [EMAIL PROTECTED] wrote: OK I'll bite. That Beginners Guide page has bugged me for a long time. It's a wiki page but it is marked as immutable so I can't change it. Here are some immediate suggestions: Good suggestions; thanks! I've applied most of them. Thanks, this is a big improvement. Here are a few more ideas: - change Next, you need to get the Python interpreter installed on your computer. to Next, install the Python interpreter on your computer. (active voice) - move and rewrite the You'll want to select a [WWW] text editor... sentence. For a raw beginner, this is not the next step and the page it links to will not be helpful. Tutorials generally start out at the interpreter prompt, not writing programs in an editor. Whatever editor is handy and familiar is probably fine for a first program when the time comes. Here is a suggested rewrite: When you are ready to write your first program you will need a text editor. To get started you can use any editor you are familiar with such as NotePad or insert names of other common editors. As you gain experience you may want to use a text editors with features that help you write Python programs. A comprehensive list is here link. I think I would put this before the paragraph beginning Once you've read a tutorial. - Move the Need to know how to run Python programs on Windows? sentence to the last bullet of the list in the next paragraph and rewrite it to Most tutorials assume you know how to run a program on your computer. If you are using Windows and need help with this, see link. - Change Next, you're going to want to read a tutorial to Next, read a tutorial With these changes the first links on this page are BG/Overview, BG/Download and BG/NonProgrammers. The second link on BG/NonProgrammers is a reasonable tutorial and the first link is pretty obviously one to skip. So a beginner is guided through the necessary steps with nothing extra or distracting or overwhelming intervening. - Change the sentence Read BeginnersGuide/Overview to learn the key points. to Read BeginnersGuide/Overview to learn what makes Python special. Or maybe get rid of it completely - I'm not sure evangelism belongs on this page. Yes, it does; fairly often the webmaster alias receives e-mails that ask so what is Python? Direct them to the What is Python? link on the front page maybe? ISTM the material in BG/Overview belongs on the pages linked from What is Python? Thanks, Kent -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get the extension of a filename from the path
Lad wrote: Thank you ALL for help Regards, L. addendum: ASPN Python cookbook often has something relevant / modifiable for your needs: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/81931 http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52661 (in this case code from 2001 / 2 is probably py 2.0 or 2.1, shd still work) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there anything that pickle + copy_reg cannot serialize?
On Thu, 08 Dec 2005 22:42:32 +0800, Maurice LING [EMAIL PROTECTED] wrote: Hi, I need to look into serialization for python objects, including codes, recursive types etc etc. Currently, I have no idea exactly what needs to be serialized, so my scope is to be as wide as possible. I understand that marshal is extended by pickle to serialize class instances, shared elements, and recursive data structures (http://www.effbot.org/librarybook/pickle.htm) but cannot handle code types. pickle can be used together with copy_reg and marshal to serialize code types as well (http://www.effbot.org/librarybook/copy-reg.htm). So my question will be, are there anything that pickle/copy_reg/marshal combination cannot serialize? If so, what are the workarounds? Since copy_reg lets you specify arbitrary code to serialize arbitrary objects, you shouldn't run into any single object that you cannot serialize to a pickle. However, both pickle implementations are recursive, so you will be limited by the amount of memory you can allocate for your stack. By default, this will limit you to something like object graphs 333 edges deep or so (if I'm counting stack frames correctly). Note that this does not mean you cannot serialize more than 333 objects at a time, merely that if it takes 333 or more steps to go from the first object to any other object in the graph (using the traversal order pickle uses), the pickling will fail. You can raise this limit, to a point, with sys.setrecursionlimit(). Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
On Wed, 07 Dec 2005 10:36:52 -0600, A.M. Kuchling [EMAIL PROTECTED] wrote: of the seealso environment. I'll talk to Fred about it and begin assembling a patch. Patch #1376361: http://www.python.org/sf/1376361 . I still need to talk to Fred about this. --amk -- http://mail.python.org/mailman/listinfo/python-list
Re: Encoding of file names
utabintarbo wrote: I am trying to programatically access files created on an IBM AIX system, stored on a Sun OS 5.8 fileserver, through a samba-mapped drive on a Win32 system. Not confused? OK, let's move on... ;-) When I ask for an os.listdir() of a relevant directory, I get filenames with embedded escaped characters (ex. 'F07JS41C.04389525AA.UPR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model') how did you print that name? \xa6 is a broken vertical bar, which, as far as I know, is a valid filename character under both Unix and Windows. if DIR is a variable that points to the remote directory, what does this print: import os files = os.listdir(DIR) file = files[0] print file print repr(file) fullname = os.path.join(DIR, file) print os.path.isfile(fullname) print os.path.isdir(fullname) (if necessary, replace [0] with an index that corresponds to one of the problematic filenames) when you've tried that, try this variation (only the listdir line has changed): import os files = os.listdir(unicode(DIR)) # -- this line has changed file = files[0] print file print repr(file) fullname = os.path.join(DIR, file) print os.path.isfile(fullname) print os.path.isdir(fullname) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Mutability of function arguments?
Mike Meyer wrote: Your description of passes references by value is a description of call by reference. C passes all arguments by value, to pass a reference, the C programmer creates the reference to the value by hand, then dereferences it by hand at the other end. So C's call-by-reference passes the reference by value. There's no difference between C's call-by-reference and Python's call-by-reference, and using different words to try and imply there is will just cause problems further on. can you guys please stop using call by value and call by reference when you discuss Python. both terms have established meanings, and Python's argument passing model doesn't match any of them. this was known some 30 years ago; here's a quote from a CLU reference manaual from 1979: We call the argument passing technique _call by sharing_, because the argument objects are shared between the caller and the called routine. This technique does not correspond to most traditional argument passing techniques (it is similar to argument passing in LISP). In particular IT IS NOT call by value because mutations of arguments per- formed by the called routine will be visible to the caller. And IT IS NOT call by reference because access is not given to the variables of the caller, but merely to certain objects. (CLU was one of the first languages to use objects in the Python sense, as well as the same argument passing model as today's Python) established terms for Python's argument passing model are call by object or call by sharing for more on this, see the comp.lang.python archives. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: how to put form and display its result(data from database) on the same window?
Hi Peter, Could you give me detailed information about your idea. Thanks, Laya -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
A.M. Kuchling wrote: of the seealso environment. I'll talk to Fred about it and begin assembling a patch. Patch #1376361: http://www.python.org/sf/1376361 . I still need to talk to Fred about this. cool. can you post a sample page somewhere? /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Documentation suggestions
amk I wonder if the Internet chapter should be split into HTTP/Web
amk Tools (webbrowser, cgi, cgitb, httplib, urllib) and Non-Web
amk Protocols (ftplib, gopherlib, smtp, all the rest).
Note that cgitb works just fine in a non-web environment. I would actually
prefer it be renamed (fancytb?) and then stuck wherever the traceback
module docs go.
\input{distutils}
amk Distutils should probably be in Program Frameworks. Or it could just
amk have a chapter of its own, or maybe there are enough modules for an
amk Application Support chapter.
There are currently 46 module index entries for the various parts of
distutils. I think it would be helpful to reduce that number a bit...
Skip
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Re: spawnle umask
In article [EMAIL PROTECTED], Yves Glodt [EMAIL PROTECTED] wrote: David Wahler wrote: Yves Glodt wrote: It does, I did like this: os.umask(0113) newpid = os.spawnl(os.P_NOWAIT,'/usr/local/bin/wine','/usr/local/bin/wine',executabl e) But I wanted to use spawnle and it's env argument, to avoid setting umask manually... The umask is not part of the environment, so there's no way to set it directly through spawnle. ok Why don't you want to use os.umask? Only because I thought spawnle could set it through env... But as it can't I will now go with os.umask. On UNIX, the spawn functions are just Python code that wraps up the low level fork and execve system calls. There's no reason you can't write your own version if you like, that does what you need. It does make sense to want to modify umask and who knows what other inheritable context in the fork, so you might be thinking of an API with a function that's called at that time, like spawnve(wait, file, args, env, func) The funny thing is, that's such a good idea that the implementation already has a function with that signature. The only difference is that func() also must call the appropriate execve function. So for example, def execumask113(file, args, env): os.umask(0113) return os.execve(file, args, env) ... os._spawnvef(os.P_NOWAIT, '/usr/local/bin/wine', ['wine', exe], os.environ, execumask113) Now the problem is that this function is evidently not part of the published API for os.py, so it would be unseemly to complain if it were to change in later versions. So I guess the right thing to do is write your own spawn function from the ground up. But at least you have some ideas there about how it might work. Donn Cave, [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Encoding of file names
Fredrik, you are a God! Thank You^3. I am unworthy /ass-kiss-mode I believe that may do the trick. Here is the results of running your code: DIR = os.getcwd() files = os.listdir(DIR) file = files[-1] file 'L07JS41C.04389525AA.QTR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model' print file L07JS41C.04389525AA.QTRªINR.EªC-P.D11.081305.P2.KPF.model print repr(file) 'L07JS41C.04389525AA.QTR\xa6INR.E\xa6C-P.D11.081305.P2.KPF.model' fullname = os.path.join(DIR, file) print os.path.isfile(fullname) False print os.path.isdir(fullname) False files = os.listdir(unicode(DIR)) file = files[-1] print file L07JS41C.04389525AA.QTR¦INR.E¦C-P.D11.081305.P2.KPF.model print repr(file) u'L07JS41C.04389525AA.QTR\u2592INR.E\u2524C-P.D11.081305.P2.KPF.model' fullname = os.path.join(DIR, file) print os.path.isfile(fullname) True --- Success! print os.path.isdir(fullname) False Thanks to all who posted. :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitching about the documentation...
Steven D'Aprano [EMAIL PROTECTED] wrote: Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo. S P O I L E R S P A C E (Good grief, I've not done that in *years*.) Buffalo from the city of Buffalo, which are intimidated by buffalo from Buffalo, also intimidate buffalo from Buffalo. I didn't say it was *good* English, but it is *legal* English. I *think* that's similar to the one I know about the cannibalistic behaviour of some oysters, which split open other oysters (to eat them). It starts: Oysters oysters split split. Oysters which oysters split become split. But there's nothing to stop a third set of oysters predating on the ones doing the splitting: Oysters oysters oysters split split split. And so on. My brain hurts too much to work out if you can do the same to the buffaloes. And here endeth today's lesson in recursion. -- \S -- [EMAIL PROTECTED] -- http://www.chaos.org.uk/~sion/ ___ | Frankly I have no feelings towards penguins one way or the other \X/ |-- Arthur C. Clarke her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitching about the documentation...
François Pinard [EMAIL PROTECTED] wrote: [AMK] You may suggest that I should process my e-mail more promptly. No, I'm not suggesting you how to work, no more that I would accept that you force me into working your way. If any of us wants to force the other to speak through robots, that one is not far from unspeakable... This is why things need to go into public trackers, or wiki pages. Whatever means the maintainer wants to fill his preservation needs, he is free to use them. The problem arises when the maintainer wants imposing his own work methods on others. Let contributors be merely contributors, and learn how to recognise contributions as such and say thank you, instead of trying to turn contributors into maintainers. Either I don't understand what you are saying or you are being a hypocrite. Andrew is saying that he doesn't have time to detail with all the messages that get sent to him personally. What do you propose he should do? I think people expect more that a message saying Thanks for you contribution. PS: Since I don't have time to do anything with it, your message will now be discarded.. Neil -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there anything that pickle + copy_reg cannot serialize?
Since copy_reg lets you specify arbitrary code to serialize arbitrary objects, you shouldn't run into any single object that you cannot serialize to a pickle. In http://www.effbot.org/librarybook/pickle.htm, it specifically mentions that code objects cannot be pickled and require the use of copy_reg, as follows: import copy_reg import pickle, marshal, types # # register a pickle handler for code objects def code_unpickler(data): return marshal.loads(data) def code_pickler(code): return code_unpickler, (marshal.dumps(code),) copy_reg.pickle(types.CodeType, code_pickler, code_unpickler) # # try it out CODE = print suppose he's got a pointed stick code = compile(CODE, string, exec) exec code exec pickle.loads(pickle.dumps(code)) I cannot understand 2 things, which I seek assistance for: 1. Is code object the only thing can cannot be pickled (less facing recursion limits)? 2. In the above example, how copy_reg works with pickle? Thanks and Cheers Maurice However, both pickle implementations are recursive, so you will be limited by the amount of memory you can allocate for your stack. By default, this will limit you to something like object graphs 333 edges deep or so (if I'm counting stack frames correctly). Note that this does not mean you cannot serialize more than 333 objects at a time, merely that if it takes 333 or more steps to go from the first object to any other object in the graph (using the traversal order pickle uses), the pickling will fail. You can raise this limit, to a point, with sys.setrecursionlimit(). Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
newby question: Splitting a string - separator
Hi all, i am having a textfile which contains a single string with names. I want to split this string into its records an put them into a list. In normal cases i would do something like: #!/usr/bin/python inp = open(file) data = inp.read() names = data.split() inp.close() The problem is, that the names contain spaces an the records are also just seprarated by spaces. The only thing i can rely on, ist that the recordseparator is always more than a single whitespace. I thought of something like defining the separator for split() by using a regex for more than one whitespace. RegEx for whitespace is \s, but what would i use for more than one? \s+? TIA, Tom -- http://mail.python.org/mailman/listinfo/python-list
Re: efficient 'tail' implementation
[EMAIL PROTECTED] wrote: hi I have a file which is very large eg over 200Mb , and i am going to use python to code a tail command to get the last few lines of the file. What is a good algorithm for this type of task in python for very big files? Initially, i thought of reading everything into an array from the file and just get the last few elements (lines) but since it's a very big file, don't think is efficient. thanks You should look at pyinotify. I assume we're talking linux here. -- http://mail.python.org/mailman/listinfo/python-list
Re: ElementTree - Why not part of the core?
[EMAIL PROTECTED] wrote: I think the key here is ElementTree's Pythoninc API. While it's clearly possible to install it as a third-party package, I think there's a clear best-of-breed aspect here that suggests it belongs in the standard distribution simply to discourage continued use of DOM-based APIs. I second this. Guido has said many times that the stdlib is for best-of-breed modules that have proven themselves in the wild. ElementTree has proven itself in the wild and is clearly best-of-breed. And dramatically better (IMHO) than the APIs currently included in the stdlib[1]. I don't have a whole lot of free time, and I'm not sure exactly how I could help, but if there's anything I could do that would help get ElementTree into the stdlib, let me know. STeVe [1] If I had my way, we'd deprecate and then remove the current Python xml modules. But of course then people would complain that Python doesn't have a SAX or DOM API. Of course we could tell them that they don't need it and that ElementTree is easier, but I'm not sure people really want to fight that battle. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to ping in Python?
You could also try the ping module that the Eddie monitoring tool has been using successfully, cross-platform, for many years. http://dev.eddie-tool.net/trac/browser/eddie/trunk/lib/common/Directives/pinger.py Cheers, Chris Nico Grubert wrote: I could not find any ping Class or Handler in python (2.3.5) to ping a machine. I just need to ping a machine to see if its answering. What's the best way to do it? -- http://chrismiles.info/ -- http://mail.python.org/mailman/listinfo/python-list
Images Connected Component labeling
Does anyone know where I can find a 'connected component' image processing function? I don't see it in numarray or scipy core... In matlab the function is called bwlabel(bw,4); and step 8 on this page is an example of what I'm trying to do: http://www.mathworks.com/access/helpdesk_r13/help/toolbox/images/getting3.html Thanks, -Jim -- http://mail.python.org/mailman/listinfo/python-list
Re: sql escaping module
Fredrik Lundh wrote: David Bear wrote: Being new to pgdb, I'm finding there are lot of things I don't understand when I read the PEP and the sparse documentation on pgdb. I was hoping there would be a module that would properly escape longer text strings to prevent sql injection -- and other things just make sure the python string object ends up being a properly type for postgresql. I've bought 3 books on postgresql and none of th code samples demonstrate this. web searchs for 'python sql escape string' yeild way too many results. Any pointers would be greatly appreciated. for x in range(100): print USE PARAMETERS TO PASS VALUES TO THE DATABASE /F Yes. Fredrik and others. Thank you for the advice. I know have the following code: .. parmChar = '%s' sqlInsert = INSERT INTO %s (%s) VALUES (%s); % (tn, , .join(fieldnames), , .join([parmChar] * len(fieldnames))) try: cursor.execute(sqlInsert, datum) except pgdb.DatabaseError: logerror(Error on record insert \n %s \n %s % (sqlInsert, traceback.print_exc())) I was not aware that the python db interface would just handle proper escaping of python data types to proper postgresql data types. Any other hints on database programming much appreciated. -- David Bear -- let me buy your intellectual property, I want to own your thoughts -- -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there anything that pickle + copy_reg cannot serialize?
On Fri, 09 Dec 2005 02:17:10 +0800, Maurice LING [EMAIL PROTECTED] wrote: Since copy_reg lets you specify arbitrary code to serialize arbitrary objects, you shouldn't run into any single object that you cannot serialize to a pickle. [snip - example of pickling code objects] I cannot understand 2 things, which I seek assistance for: 1. Is code object the only thing can cannot be pickled (less facing recursion limits)? No. There are lots of objects that cannot be pickled by default. Any extension type which does not explicitly support it cannot be pickled. Generators cannot be pickled. Method descriptors can't be pickled. Et cetera. 2. In the above example, how copy_reg works with pickle? Any time pickle thinks it has found something it cannot pickle, it asks the copy_reg module for some help. The above example basically teaches the copy_reg module how to give the pickle module the help it needs for code objects. Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: newby question: Splitting a string - separator
Thomas Liesner wrote:
Hi all,
i am having a textfile which contains a single string with names.
I want to split this string into its records an put them into a list.
In normal cases i would do something like:
#!/usr/bin/python
inp = open(file)
data = inp.read()
names = data.split()
inp.close()
The problem is, that the names contain spaces an the records are also
just seprarated by spaces. The only thing i can rely on, ist that the
recordseparator is always more than a single whitespace.
I thought of something like defining the separator for split() by using
a regex for more than one whitespace. RegEx for whitespace is \s, but
what would i use for more than one? \s+?
TIA,
Tom
\s+ gives one or more, you need \s{2,} for two or more:
import re
re.split(\s{2,},Guido van Rossum Tim Peters Thomas Liesner)
['Guido van Rossum', 'Tim Peters', 'Thomas Liesner']
Michael
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Re: newby question: Splitting a string - separator
Thomas Liesner wrote:
...
The only thing i can rely on, ist that the
recordseparator is always more than a single whitespace.
I thought of something like defining the separator for split() by using
a regex for more than one whitespace. RegEx for whitespace is \s, but
what would i use for more than one? \s+?
For your split regex you could say
\s\s+
or
\s{2,}
This should work for you:
YOUR_SPLIT_LIST = re.split(\s{2,}, YOUR_STRING)
Yours,
Noah
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Re: newby question: Splitting a string - separator
Hi Tom, a regex for more than one whitespace. RegEx for whitespace is \s, but what would i use for more than one? \s+? For more than one, I'd use \s\s+ -Jim -- http://mail.python.org/mailman/listinfo/python-list
Re: unittest and non-.py files
[Michael Hoffman] Hi. I am trying to use unittest to run a test suite on some scripts that do not have a .py extension. [Sybren Stuvel] I'd move the functionality of the script into a separate file that does end in .py, and only put the invocation into the .py-less script. That's what I have done, and it is a better solution for other reasons. Thanks Sybren. I would still like to do what I originally proposed. Would this warrant a feature request? -- Michael Hoffman -- http://mail.python.org/mailman/listinfo/python-list
Re: what's wrong with lambda x : print x/60,x%60
Steve Holden wrote: Paul Rubin wrote: I think it's a Python weakness that you can't declare a local var like in other languages, to go out of scope at the end of the current block, e.g.: if cond: my x = 7# make a new scope for x, goes out of scope at end of if If this genuinely troubles you then you can always isolate the scope with a function, though of course you also no longer have the code inline then. Or, if you must: def called(function): function() return called then: @called def called(): whatever ;-) -- -Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: how to put form and display its result(data from database) on the same window?
[EMAIL PROTECTED] wrote: Could you give me detailed information about your idea. I believe I just did. Really, as I said, this is non-trivial. I can't give you a three minute tutorial that will help you at all, especially if you haven't read the information I pointed you to. (The page I pointed you to actually links to the following one, in case you didn't notice: http://en.wikipedia.org/wiki/Ajax_%28programming%29 ) -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Post-modernism, Academia, and the Tech Geeking fuckheads
I don't know about anyone else, but you'd impress me much more if you didn't swear in your posts. I am personally not offended, but it does lower your credibility in my eyes. Just a tip. Brad -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitching about the documentation...
The actress Margaret Anglin left this note in the dressing froom of another actress: 'Margaret Anglin says Mrs. Fiske is the best actress in America.' Mrs. Fiske added two commas and returned the note: 'Margaret Anglin, says Mrs. Fiske, is the best actress in America.' Or this, from a George Will column: Huge doctrinal consequences flow from the placing of a comma in what Jesus, when on the cross, said to the thief (Luke 23:43): 'Verily, I say unto thee, This day thou shalt be with me in Paradise' or 'Verily, I say unto thee this day, Thou shalt be with me in Paradise.' The former leaves little room for purgatory. -- http://mail.python.org/mailman/listinfo/python-list
Re: what's wrong with lambda x : print x/60,x%60
Steve Holden [EMAIL PROTECTED] writes: if cond: my x = 7# make a new scope for x, goes out of scope at end of if If this genuinely troubles you then you can always isolate the scope with a function, though of course you also no longer have the code inline then. I don't generally speaking see the point: The point is something like: it's normal to write if cond: x = 7 do_something_with(x) # now you don't care about x any more. Years later, there's some production problem in the middle of the night and someone has to put in a patch, and they re-use the value in x for something later in the function, i.e. y = x + 3# since x is still in scope from way up there and check it in. Years after THAT, yet another person re-uses the name x for something, etc. Yeah, yeah, bad programming practice, blah, blah, blah, but anyone who's maintained code in the real world knows this stuff happens all the time. Well, as warts go the inability to tightly control the scope of variables isn't really that terrible, is it? I wouldn't say it's as terrible as some things might be, but it contributes to a sense of sloppiness about Python, that there are always all these dirty dishes laying around. Even the encrustation we call Perl doesn't have this problem; it can not only control scope, but it has the -T (taint checking) feature that analyzes actual dataflow from one variable to another and flags you if you do something dangerous with unchecked user input. This turns out to be very useful. I wish Python had something like it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Unexpected behavior of read only attributes and super
P.S. Note that there is an additional complication resulting from the
fact that functions are descriptors:
class C(dict):
... pass
...
C.__iter__
slot wrapper '__iter__' of 'dict' objects
C().__iter__
method-wrapper object at 0x00E74A10
Even though the C instance is accessing the __iter__ function on the
class, it gets back a different value because descriptors return
different values depending on whether they are accessed from a
class or
an instance. I don't think you need to understand this to solve your
problem though, so I won't go into any more details unless you
think it
would be helpful.
I found your explanation very helpful. After reading it I went back
and read
my Nutshell book and realized that the explanation was in there but I
didn't get it until now.
Although I did find an exception to the rule for attribute writes.
(See !Whoops below)
If you would care to elaborate on the how the lookup differs with
method descriptor
it would be most appreciated. Mostly because it seems that having
slots defined
changes the method lookup as opposed to the variable lookup and
apparently some of the type class
variables are special enough that they have their own rules.
This might help explain why it is that when I define __slots__, the
behavior when writing an attribute is different for
attributes that exist in the class versus attributes that exist in
__slots__ versus attributes that
do not exist at all. It is also different if the class attribute is a
method vesus a variable.
For example
class C(dict):
... __slots__ = ['a','b']
...
c = C()
c.a
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: a
So slot defined but not assigned gets error
c.a = 5
c.a
5
OK here
c.c
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object has no attribute 'c'
Surprise error gives no clue that slots is the reason for the error
c.c = 4
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object has no attribute 'c'
ditto
Now the behavior is different for class variables and methods when
slots defined
versus when slots is not defined.
c.__iter__ = 4
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object attribute '__iter__' is read-only
super(C,c).__iter__ = 4
Traceback (most recent call last):
File stdin, line 1, in ?
TypeError: 'super' object has only read-only attributes (assign
to .__iter__)
c.__class__ = C
c.__class__
class '__main__.C'
it let me assign it! But not shadowed
c.__dict__
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object has no attribute '__dict__'
!Whoops now I am confused again. Didn't you say
When writing an attribute (i.e. using the assignment statement),
Python does not try to do any namespace searching. Thus if you use
the
instance in an assignment statement, then it is the instance's
attributes that get modified, and if you use the class in an
assignment
statement, then it is the class's attributes that get modififed:
Then why wasn't __class__ added to c.__dict__ ? Looks like namespace
searching to me.
So to cross check if slots is not defined
class C(dict):
... pass
...
c = C()
c.__iter__ = 1
c.__dict__
{'__iter__': 1}
c.__class__ = C
c.__dict__
{'__iter__': 1}
try again a different way
class B(C):
... pass
...
c.__class__ = B
c.__dict__
{'__iter__': 4}
OK but maybe __class__ is magic, so I tried again
class C(dict):
... a = 0
...
c = C()
c.a
0
c.a = 4
c.__dict__
{'a': 4}
OK __class__ is special
now with slots defined
class C(dict):
... __slots__ = ['b']
... a = 0
...
c = C()
c.a
0
c.a = 4
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object attribute 'a' is read-only
C.a = 5
c.a
5
So the rule is that when __slots__ is defined class variables become
read only.
What if the class variable is included in __slots__
class C(dict):
... __slots__ = ['b']
... b = 1
...
c = C()
c.b
1
c.b = 2
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'C' object attribute 'b' is read-only
So even though b is in slots I still can't create an instance
variable by that name
and shadow the class variable.
It feels like the implementation of slots is half baked.
Finally
Since the way of python is that if an object does not have an
attribute
but you can assign it one then it creates one dynamically (in the
same 'way' that if a variable does not
exist is creates one upon assignment).
Because slots break this paradigm then at the very least the error
messages should point out that this object
is using slots so beware.
For example I would prefer something like the following
c.a
AttributeError: Slot 'a' not yet assigned
c.c
AttributeError: No slot named 'c' on instance
c.c = 4
