Re: return None
Ximo [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] Can I do a function which don't return anything? No, if you mean like subroutines. The question is that, if I do a function that have a return or without return, it returns always None, but i want that it doesnt return me nothing Why? An answer to that would help you maybe get better answers here. Terry J. Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
John Machin wrote:
Reinhold Birkenfeld wrote:
Berthold Höllmann wrote:
Francois De Serres [EMAIL PROTECTED] writes:
hiho,
what's the clean way to translate the tuple (0x73, 0x70, 0x61, 0x6D)
to the string 'spam'?
. t = (0x73, 0x70, 0x61, 0x6D)
. ''.join('%c' % c for c in t)
'spam'
Or:
t = (0x73, 0x70, 0x61, 0x6D)
('%c' * len(t)) % t
You don't need the sissy parentheses; '%c' * len(t) % t works just fine :-)
Ah, ok. Didn't want to lookup the precedence rules...
Reinhold
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unit test nested functions
How can you unit test nested functions? Or do you have to pull them out to unit test them, which basically means I will never use nested functions. Also, same thing with private member functions protected by __. Seems like there is a conflict there between using these features and unit testing. Andy -- http://mail.python.org/mailman/listinfo/python-list
Re: return None
Grant Edwards wrote: [snip..] Personally, I don't really like the idea that falling off the botton of a function implicitly returns None. It's just not explicit enough for me. My preference would be that if the function didn't execute a return statement, then it didn't return anyting and attempting to use a return value would be an error. I suppose there probably is code out there that depends on the implicit return None at the end of every function, so it's too late to change things now. Yeah - I frequently rely on that behaviour, but purely our of laziness. Best Regards, Fuzzy http://www.voidspace.org.uk/python -- Grant Edwards grante Yow! Is it FUN to be at a MIDGET? visi.com -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP on path module for standard library
Andrew Dalke [EMAIL PROTECTED] wrote: [snipped] Take for example the case where a PhoneNumber class is subclass of int. According to LSP, it is perfectly ok to add phone numbers together, subtract them, etc, but the result, even if it's a valid phone number, just doesn't make sense. Mmm, I don't think an integer is a good model of a phone number. For example, in the US 00148762040828 will ring a mobile number in Sweden while 148762040828 will give a this isn't a valid phone number message. That's why phone numbers would be a subset of integers, i.e. not every integer would correspond to a valid number, but with the exception of numbers starting with zeros, all valid numbers would be an integers. Regardless, this was not my point; the point was that adding two phone numbers or subtracting them never makes sense semantically. [snipped] I just noted that conceptually a path is a composite object consisting of many properties (dirname, extension, etc.) and its string representation is just one of them. Still, I'm not suggesting that a 'pure' solution is better that a more practical that covers most usual cases. For some reason I think that path.dirname() is better than path.dirname Python has properties now so the implementation of the latter is trivial - put a @property on the line before the def dirname(self):. Sorry, I used the term 'property' in the broad sense, as the whole exposed API, not the specific python feature; I've no strong preference between path.dirname and path.dirname(). I think that the string representation of a path is so important that it *is* the path. There are (at least) two frequently used path string representations, the absolute and the relative to the working directory. Which one *is* the path ? Depending on the application, one of them woud be more natural choice than the other. I trust my intuition on this, I just don't know how to justify it, or correct it if I'm wrong. My intuition also happens to support subclassing string, but for practical reasons rather than conceptual. George -- http://mail.python.org/mailman/listinfo/python-list
Re: return None
Grant Edwards wrote: Personally, I don't really like the idea that falling off the botton of a function implicitly returns None. It's just not explicit enough for me. My preference would be that if the function didn't execute a return statement, then it didn't return anyting and attempting to use a return value would be an error. That's not a bad idea. I tend to prefer self-documenting code whenever possible anyway, so if I a method ends that I don't intend to have a useful return value, I don't have a return statement with an argument, and if I intend a method that returns a useful value to return one that might be None, I do so expliclitly, rather than having the logic fall off the end of the function, making it unclear what was intended in the first place. -- Erik Max Francis [EMAIL PROTECTED] http://www.alcyone.com/max/ San Jose, CA, USA 37 20 N 121 53 W AIM erikmaxfrancis Grab a club and join the chorus / Evolution is a state of mind -- Oleta Adams -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP on path module for standard library
George Sakkis wrote: That's why phone numbers would be a subset of integers, i.e. not every integer would correspond to a valid number, but with the exception of numbers starting with zeros, all valid numbers would be an integers. But it's that exception which violates the LSP. With numbers, if x==y then (x,y) = (y,x) makes no difference. If phone numbers are integers then 001... == 01... but swapping those two numbers makes a difference. Hence they cannot be modeled as integers. Regardless, this was not my point; the point was that adding two phone numbers or subtracting them never makes sense semantically. I agree. But modeling them as integers doesn't make sense either. Your example of adding phone numbers depends on them being represented as integers. Since that representation doesn't work, it makes sense that addition of phone number is suspect. There are (at least) two frequently used path string representations, the absolute and the relative to the working directory. Which one *is* the path ? Depending on the application, one of them woud be more natural choice than the other. Both. I don't know why one is more natural than the other. I trust my intuition on this, I just don't know how to justify it, or correct it if I'm wrong. My intuition also happens to support subclassing string, but for practical reasons rather than conceptual. As you may have read elsewhere in this thread, I give some examples of why subclassing from string fits best with existing code. Even if there was no code base, I think deriving from string is the right approach. I have a hard time figuring out why though. I think if the lowest level Python/C interface used a get the filename interface then perhaps it wouldn't make a difference. Which means I'm also more guided by practical reasons than conceptual. Andrew [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Difference between and '
On Fri, 22 Jul 2005 08:38:28 -0400, Peter Hansen wrote: Steven D'Aprano wrote: It may shock some people to learn that difference in the sense of mathematical subtraction is not the only meaning of the word, but there it is. One wouldn't, I hope, misunderstand What is the difference between spaghetti marinara and spaghetti pescatora? and attempt to subtract one from the other, since subtraction is not defined for foodstuffs. sum(ord(c) for c in 'spaghetti marinara') - sum(ord(c) for c in spaghetti pescatora) -119 Works for me... ;-) Yes, but if you had thought about the problem a little longer, you would have removed the spaghetti from both, since they just cancel each other. Although that does assume that the commutative law holds for pasta products. Personally, I prefer this answer: import sets sets.Set(spaghetti marinara) - sets.Set(spaghetti pescatora) Set(['m', 'n']) -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
On Fri, 22 Jul 2005 06:07:28 -0700, Robert Kern wrote: Francois De Serres wrote: hiho, what's the clean way to translate the tuple (0x73, 0x70, 0x61, 0x6D) to the string 'spam'? In [1]: t = (0x73, 0x70, 0x61, 0x6D) In [2]: ''.join(chr(x) for x in t) Out[2]: 'spam' I get a syntax error when I try that. I guess anyone who hasn't started using Python 2.4 will also get the same error. Since t is just a tuple, there isn't a big advantage as far as I can see to build up and dispose of the generator machinery just for grabbing the next item in a tuple. So a list comprehension will work just as well, and in older versions of Python: ''.join([chr(x) for x in (0x73, 0x70, 0x61, 0x6D)]) For an even more version-independent method: L = [] for n in (0x73, 0x70, 0x61, 0x6D): L.append(chr(n)) print ''.join(L) or even: ''.join(map(lambda n: chr(n), (0x73, 0x70, 0x61, 0x6D))) 'spam' -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: unit test nested functions
Andy wrote: How can you unit test nested functions? I can't think of a good way. When I write a nested function it's because the function uses variables from the scope of the function in which it's embedded, which means it makes little sense to test it independent of the larger function. My tests in that case are only of the enclosing function. Or do you have to pull them out to unit test them, which basically means I will never use nested functions. You don't test every line in a function by itself, right? Nor every loop in a function. It should be possible to test the outer function enough that the implementation detail - of using an inner function - doesn't make much difference. Also, same thing with private member functions protected by __. Seems like there is a conflict there between using these features and unit testing. In that case the spec defined that the real function name is of the form _CLASSNAME__METHODNAME. For example class Spam: ... def __sing(self): ... print I don't see any Vikings. ... spam = Spam() spam._Spam__sing() I don't see any Vikings. I've found though that the double-leading-underscore is overkill. Using a single underscore is enough of a hint that the given method shouldn't be called directly. Then again, I don't write enough deep hierarchies where I need to worry about a subclass implementation using the same private name as a superclass. Andrew [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: is this possible?
On Fri, 22 Jul 2005 07:59:42 -0700, scrimp wrote: I am using reportlab not to generate PDF files, Isn't that amazing! I'm also using reportlab not to generate PDF files too! I installed the program, and it just sits there, not generating as many PDF files as I don't want for as long as I don't want them. :-) but I want to be able to print them without having to install acrobat reader. I looked through the users guide and found nothing about printing to a printer (programmatically). I want to be able to automate the printing of reports when they are available. Does anyone know how this is done using reportlab? thanks! As others have suggested, if you have to deal with PDF files without Acrobat, you could use ghostscript. Also pre-installed on many versions of Linux, and probably other Unixes as well, is pdf2ps which will convert the PDF file to a pure postscript file, which you can then print to any printer which understands postscript. If you are using Windows, you can possibly find open source or free software to do these things. Google is your friend: www.google.com But the chances are you'll have to install *something* -- compared to even the most impoverished Linux distro, Windows is very much batteries not included, and while Python does come with many batteries, a full-blown postscript interpreter is not one of them. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Neat access to db query results
Hi,
I often wish for a really high-level way to access db results, being
willing to forego some efficiency. I came up with a class you can use
like:
cur = db.cursor()
cur.execute('select abc, def from blah')
for row in dbcur_iter(cur):
print row['abc'], row['def']
Here's the class:
class dbcur_iter:
def __init__(self, cur):
self.cur = cur
self.names = [x[0] for x in cur.description]
def __iter__(self):
return self
def next(self):
x = cur.fetchone()
if x is None:
raise StopIteration
return dict(zip(self.names, x))
Hope you find it useful! Do send me any feedback.
Paul
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Getting a dictionary from an object
Hello. I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. The following works, but I would prefer to use a built-in way if one exists. Is there one? Thanks in advance. class dictobj(dict): class dictobj(dict): A dictionary d with an object attached to it, which treats d['foo'] as d.obj.foo. def __init__(self, obj): self.obj = obj def __getitem__(self, key): return self.obj.__getattribute__(key) -- Thanos Tsouanas .: My Music: http://www.thanostsouanas.com/ http://thanos.sians.org/ .: Sians Music: http://www.sians.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Thanos Tsouanas a écrit : Hello. I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. The following works, but I would prefer to use a built-in way if one exists. Is there one? Thanks in advance. class dictobj(dict): class dictobj(dict): A dictionary d with an object attached to it, which treats d['foo'] as d.obj.foo. def __init__(self, obj): self.obj = obj def __getitem__(self, key): return self.obj.__getattribute__(key) I'd replace this last line with: return getattr(self.obj, key) Now given your specs, I don't see what's wrong with your solution. -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Thanos Tsouanas wrote: Hello. I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. The following works, but I would prefer to use a built-in way if one exists. Is there one? class dictobj(dict): class dictobj(dict): A dictionary d with an object attached to it, which treats d['foo'] as d.obj.foo. def __init__(self, obj): self.obj = obj def __getitem__(self, key): return self.obj.__getattribute__(key) use getattr(self.obj,key) possibly, as __getattribute__ gets total control on attribute access ___ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it -- http://mail.python.org/mailman/listinfo/python-list
SPE Ide Crash
Hi Stani, Downloaded your latest SPE editor 0.7.4.m . I'm running wxPython 2.6.1 on a Fedora Core 4 machine. The IDE is great but guess what it crashes without warning. Was typing some code and boom the whole thing disappeared without a trace. Thought should let you know All you guys using this IDE has it ever crashed on you like this??? -- http://mail.python.org/mailman/listinfo/python-list
Re: Separation of Code in CGI App
Rob Cowie a écrit : Hi, I need to create a planner/calendar system using python cgi scripts. It is my first CGI app (beyond a few tutorial examples). (snip) You may want to have a look at the cgi_app mini-framework: - http://thraxil.org/code/cgi_app/ It's a port of a Perl framework, and it has some unpythonic flavour in some points (but that can be easily corrected), and it can work with CGI and mod_python. It's quite easy to get started with, and the source being really small (about 1kloc IIRC), it's quite easy to customize to your own needs (I rolled my own mod_python-only/SimpleTAL-only version in half a day...). You also have the choice between 2 template systems, one that's dirty as can be IMHO (htmltmpl) and one that is quite nice (SimpleTAL). The only wart with SimpleTAL is that it requires every input to be unicode, but that's easy to solve also (I wrote a wrapper class that handle this quite transparently - it's still QD but works well so far, I can publish it if anyone is interested). My 2 cents -- http://mail.python.org/mailman/listinfo/python-list
Re: Aliasing an object's __str__ to a different method
Little less ugly: In [12]:class A(object): : def __str__(self):return self.__str__() : def str(self):return 'ciao' : def setStr(self):self.__str__=self.str : In [13]:a=A() In [14]:a.setStr() In [15]:str(a) Out[15]:'ciao' The point is str(ob) builtin looks like calling ob.__class__.__str__(ob).Prolly Python-dev is the good place to ask about. ___ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it -- http://mail.python.org/mailman/listinfo/python-list
[path-PEP] Path inherits from basestring again
Hi,
the arguments in the previous thread were convincing enough, so I made the
Path class inherit from str/unicode again.
It still can be found in CVS:
/python/nondist/sandbox/path/{path.py,test_path.py}
One thing is still different, though: a Path instance won't compare to a regular
string.
Other minor differences, as requested on python-dev, are:
* size property - getsize() method.
* atime/mtime/ctime properties - atime()/mtime()/ctime() methods
* dirname() method - directory property
* no parent property
* basename() method - basename property
* no name property
* listdir() method - children() method
* there is still a listdir() method, but with the semantics of os.listdir
* dirs() method - subdirs() method
* joinpath() method - added alias joinwith()
* splitall() method - parts() method
* Default constructor: Path() == Path(os.curdir)
* staticmethod Path.getcwd() - Path.cwd()
* bytes() / lines() / text() - read_file_{bytes,lines,text} methods
* write_{bytes,lines,text} - write_file_{bytes,lines,text} methods
These may be removed though.
Reinhold
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Re: Getting a dictionary from an object
On Sat, Jul 23, 2005 at 12:06:57PM +0200, Paolino wrote: use getattr(self.obj,key) possibly, as __getattribute__ gets total control on attribute access Thanks, but what do you mean by 'total control'? -- Thanos Tsouanas .: My Music: http://www.thanostsouanas.com/ http://thanos.sians.org/ .: Sians Music: http://www.sians.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
On Sat, Jul 23, 2005 at 11:30:19AM +0200, Bruno Desthuilliers wrote: Thanos Tsouanas a écrit : class dictobj(dict): class dictobj(dict): A dictionary d with an object attached to it, which treats d['foo'] as d.obj.foo. def __init__(self, obj): self.obj = obj def __getitem__(self, key): return self.obj.__getattribute__(key) I'd replace this last line with: return getattr(self.obj, key) Now given your specs, I don't see what's wrong with your solution. I just dont want to use my class, if one already exists in the libraries (or any other way to achieve the same thing), that's all ;) Thanks for the tip. -- Thanos Tsouanas .: My Music: http://www.thanostsouanas.com/ http://thanos.sians.org/ .: Sians Music: http://www.sians.org/ -- http://mail.python.org/mailman/listinfo/python-list
Returned mail: see transcript for details
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Retrive file name from the window's file path
Dear All, I am using Python 2.4 in the linux platform. At present I am working on webbased file manager. When I try to upload a file from the linux cgi script easily fetch the file name by the filefield.filename. But When I try to upload a file from the windows machine It won't retrieve the file instead of retrieved full path (C:\\WINDOWS\my.gif). And at the same I couldn't know how to get file name from window's file path C:\\WINDOWS\my.gif. I try to workout these things by os.path.basename().os.path.splitext(). Kindly let me how to handle these situation prabahar __ How much free photo storage do you get? Store your friends 'n family snaps for FREE with Yahoo! Photos http://in.photos.yahoo.com -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
Steven D'Aprano wrote: On Fri, 22 Jul 2005 06:07:28 -0700, Robert Kern wrote: ... or even: ''.join(map(lambda n: chr(n), (0x73, 0x70, 0x61, 0x6D))) 'spam' This is exactly what is wrong with lambda. It yearns for over-use. This last should be: ''.join(map(chr, (0x73, 0x70, 0x61, 0x6D))) --Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Thanos Tsouanas wrote:
On Sat, Jul 23, 2005 at 12:06:57PM +0200, Paolino wrote:
use getattr(self.obj,key) possibly, as __getattribute__ gets total
control on attribute access
Thanks, but what do you mean by 'total control'?
Probably nothing to do with your question :(
But:
class A(object):
... def __getattr__(self,attr):
... return 'whatever'
...
a=A()
a.b
'whatever'
getattr(a,'b')
'whatever'
a.__getattribute__('b')
Traceback (most recent call last):
File stdin, line 1, in ?
AttributeError: 'A' object has no attribute 'b'
This can probably touch you if your objects uses defualt searching for
attributes.
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Re: Aliasing an object's __str__ to a different method
Jeffrey E. Forcier wrote: ... However, you appear to be correct, and the docs appear to be confused: class MyClass(object): def edit(self): return I'm in edit mode def setEdit(self): MyClass.__str__ = self.edit ... Either way, guess I will have to take another route. Your suggestion is what I'd had in mind, and does the job pretty well. I'm still attempting to figure out the best approach to my overall problem, however, so who knows where I will end up =) Here is one more standard way to do this: class MyClass(object): ... # Common behavior goes here def setEdit(self): self.__class__ = MyEditClass def setView(self): self.__class__ = MyViewClass class MyEditClass(MyClass): def __repr__(self): return I, %s, am being edited % super( MyEditClass, self).__repr__() class MyViewClass(MyClass): def __repr__(self): return I, %s, am being viewed % super( MyViewClass, self).__repr__() Be a little careful about the structure of the subclasses (MyViewClass and MyEditClass) since they can wink into and out of existence, and all will go well. Plus, you can easily override base behavior in the subclasses differentially. Note: for this example, you could also define the methods like: class MyEditClass(MyClass): def __repr__(self): return I, %s, am being edited % MyClass.__repr__(self) When to use super rather than direct access to the superclass is an involved discussion. --Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Thanos Tsouanas a écrit : On Sat, Jul 23, 2005 at 12:06:57PM +0200, Paolino wrote: use getattr(self.obj,key) possibly, as __getattribute__ gets total control on attribute access Thanks, but what do you mean by 'total control'? mode=screamin jay hawkins __getattribute__ is really some kind of an evil black voodoo mumbo jumbo juju magic method... /mode More seriously: __getattr__() (if defined) is called when and if the 'normal' attribute lookup process failed. It's main use is to delegate attribute access to a proxied/wrapped/decorated object. __getattribute__() (if defined) completely override the attribute lookup process - so it gets full control over attribute access. This does not directly concern what you're doing now, but still, for a number of reasons, the canonical pythonic way to do named attribute access is with the builtin getattr() function, that will call on the appropriate lookup mechanism. As a general rule, '__magic__' methods are implementation, not API, so you shouldn't call on them directly unless you have a relly god reason to do so. HTH Bruno -- http://mail.python.org/mailman/listinfo/python-list
Re: Reading network interface data in linux
On Wed, 13 Jul 2005 11:09:57 +0300, Edvard Majakari [EMAIL PROTECTED] wrote:
Suppose one wants to fetch the following data from given network interface,
say, eth0:
Ethinf('eth0').addr()
'192.168.1.42/24'
...
Ethstat('eth0').rx_bytes()
14325235341223
...
One could implement modules by installing eg. ethtool and reading speed/duplex
information by parsing ethtool output, but it is ugly way to do it, prone to
errors, requires launching a process as well as installation of ethtool.
On the other hand, I have a hunch that the interface that ethtool uses is
unstable, changes between major kernel versions, varies with the kind of
hardware you have, etc.
If that is the case, you might want to keep parsing ethtool's output. Letting
/them/ worry about tracking kernel changes would actually be the most stable
solution. The ethtool authors are kernel developers, and probably know all
that stuff.
Or convince the ethtool authors to release future ethtool versions as a
Python module with an optional command-line interface ;-)
/Jorgen
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Windows Porting Help Requested
I am preparing to release an extension module that interfaces Python to the Class Library for Numbers (http://www.ginac.de/CLN/). This module will provide Python types for arbitrary precision floating point numbers, rational numbers, and their complex counterparts. The module also includes most of the functions found in the Python math and cmath libraries. This module will be useful in applications where gmpy (http://gmpy.sourceforge.net/) doesn't have enough capability (e.g. extended precision trig, complex numbers, etc.). I would like to make this module available to Windows users but have neither the development environment nor the interest to get the module to build for the standard Python distribution. I am requesting the help of a developer who is familiar with building extension modules and understands C++ porting issues. I don't think my code is the issue, since it builds with distutils. However, it depends on two libraries (CLN and GMP) that look like they have porting issues to a Windows platform. I suspect they can be made to work with some of the GNU tools on Windows. The challenge is making an extension module that contains all the required parts for the standard Python distribution. If you are a developer with the required skills and the time, I would appreciate your help. -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
On Sat, 23 Jul 2005 11:48:27 +0300, Thanos Tsouanas wrote:
Hello.
I would like to have a quick way to create dicts from object, so that a
call to foo['bar'] would return obj.bar.
That looks rather confusing to me. Why not just call obj.bar, since it
doesn't look like you are actually using the dictionary at all?
The following works, but I would prefer to use a built-in way if one
exists. Is there one?
Thanks in advance.
class dictobj(dict):
class dictobj(dict):
A dictionary d with an object attached to it,
which treats d['foo'] as d.obj.foo.
def __init__(self, obj):
self.obj = obj
def __getitem__(self, key):
return self.obj.__getattribute__(key)
I don't think this is particularly useful behaviour. How do you use it?
py D = dictobj(hello world)
py D
{}
py D.obj
'hello world'
py D[food] = spam
py D
{'food': 'spam'}
py D[food]
Traceback (most recent call last):
File stdin, line 1, in ?
File stdin, line 5, in __getitem__
AttributeError: 'str' object has no attribute 'food'
--
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Re: find a specified dictionary in a list
On Fri, 22 Jul 2005 12:42:04 +, Odd-R. wrote:
On 2005-07-22, John Machin [EMAIL PROTECTED] wrote:
Odd-R. wrote:
I have this list:
[{'i': 'milk', 'oid': 1}, {'i': 'butter', 'oid': 2},{'i':'cake','oid':3}]
All the dictionaries of this list are of the same form, and all the oids
are distinct. If I have an oid and the list, how is the simplest way of
getting the dictionary that holds this oid?
Instead of keeping a list of dictionaries, keep a dict of dicts, indexed
by the oid:
D = {1: {'i': 'milk'}, 2: {'i': 'butter'}, 3: {'i': 'cake'}}
Then you can extract a dictionary with a single call:
thedict = D[oid]
or just grab the item you want directly:
food = D[oid]['i']
No mess, no fuss. Ninety percent of the work is choosing your data
structures correctly.
Something like this:
def oidfinder(an_oid, the_list):
for d in the_list:
if d['oid'] == an_oid:
return d
return None
# These are not the oids you are looking for.
Thank you for your help, but I was hoping for an even simpler
solution, as I am suppose to use it in a
tal:block tal:define=p python: sentence.
I don't understand what that means. Can you explain please?
--
Steven.
--
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Re: PEP on path module for standard library
Michael Hoffman wrote: Reinhold Birkenfeld wrote: Probably as Terry said: a path is both a list and a string. [...] One way to divide this is solely based on path separators: ['c:', 'windows', 'system32:altstream', 'test.dir', 'myfile.txt.zip:altstream'] I would argue that any proposed solution has to work with VMS pathnames. ;-) The current stdlib solution, os.path.splitext(os.path.splitext(filename) [0])[0] is extremely clunky, and I have long desired something better. (OK, using filename.split(os.extsep) works a little better, but you get the idea.) And also with unusual (eg. RISC OS) filename extensions. To do any justice to the existing solutions, any PEP should review at least the following projects: * The path module (of course): http://www.jorendorff.com/articles/python/path/ * The py.path module (or at least the ideas for it): http://codespeak.net/py/current/doc/future.html * itools.uri http://www.ikaaro.org/itools * Results from the Object-Oriented File System Virtualisation project in the Summer of Code programme: http://wiki.python.org/moin/SummerOfCode And I hope that the latter project is reviewing some of the other work, if only to avoid the framework proliferation that people keep complaining about. Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
Steven D'Aprano wrote: ''.join(map(lambda n: chr(n), (0x73, 0x70, 0x61, 0x6D))) 'spam' Why the verbal diarrhoea? What's wrong with the (already posted) ''.join(map(chr, (0x73, 0x70, 0x61, 0x6D))) ??? -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
Reinhold Birkenfeld wrote:
John Machin wrote:
Reinhold Birkenfeld wrote:
Berthold Höllmann wrote:
Francois De Serres [EMAIL PROTECTED] writes:
hiho,
what's the clean way to translate the tuple (0x73, 0x70, 0x61, 0x6D)
to the string 'spam'?
. t = (0x73, 0x70, 0x61, 0x6D)
. ''.join('%c' % c for c in t)
'spam'
Or:
t = (0x73, 0x70, 0x61, 0x6D)
('%c' * len(t)) % t
You don't need the sissy parentheses; '%c' * len(t) % t works just fine :-)
Ah, ok. Didn't want to lookup the precedence rules...
Look up the precedence rules? Are you aware of any language where * /
and % _don't_ have the same precedence??
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Re: tuple to string?
John Machin wrote: Reinhold Birkenfeld wrote: Ah, ok. Didn't want to lookup the precedence rules... Look up the precedence rules? Are you aware of any language where * / and % _don't_ have the same precedence?? Given that % is somewhat more esoteric, I certainly have never committed to memory its position in a precedence hierarchy of *any* language. -- Robert Kern [EMAIL PROTECTED] In the fields of hell where the grass grows high Are the graves of dreams allowed to die. -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Reinhold Birkenfeld wrote:
One thing is still different, though: a Path instance won't compare to a
regular
string.
Could you please expand on what this means? Are you referring to doing
and = type operations on Paths and strings, or == and != or all those
or something else entirely?
Other minor differences, as requested on python-dev, are:
* size property - getsize() method.
* atime/mtime/ctime properties - atime()/mtime()/ctime() methods
What does this mean? The .size property and a getsize() method both
already exist (in my copy of path.py anyway) and do the same thing.
Same with the other ones mentioned above. Is someone working from an
out-of-date copy of path.py?
* dirs() method - subdirs() method
Given that .files() exists, and returns a list of the files contained in
a path which represents a folder, why would one want to use subdirs()
instead of just dirs() to do the same operation for contained folders?
If subdirs() is preferred, then I suggest subfiles() as well. Otherwise
the change seems arbitrary and ill-conceived.
* joinpath() method - added alias joinwith()
* splitall() method - parts() method
This reminds me of the *one* advantage I can think of for not
subclassing basestring, though it still doesn't make the difference in
my mind: strings already have split(), so Jason had to go with
splitpath() for the basic split operation to avoid a conflict. A
minor wart I guess.
* Default constructor: Path() == Path(os.curdir)
To construct an empty path then one can still do Path('') ?
* staticmethod Path.getcwd() - Path.cwd()
* bytes() / lines() / text() - read_file_{bytes,lines,text} methods
* write_{bytes,lines,text} - write_file_{bytes,lines,text} methods
Under Linux isn't it possible to open and read from directories much as
with files? If that's true, the above would seem to conflict with that
in some way. As with the the .subdirs() suggestion above, these changes
seem to me somewhat arbitrary. .bytes() and friends have felt quite
friendly in actual use, and I suspect .read_file_bytes() will feel quite
unwieldy. Not a show-stopper however.
-Peter
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Re: PEP on path module for standard library
George Sakkis wrote: Andrew Dalke [EMAIL PROTECTED] wrote: I think that the string representation of a path is so important that it *is* the path. There are (at least) two frequently used path string representations, the absolute and the relative to the working directory. Which one *is* the path ? Depending on the application, one of them woud be more natural choice than the other. Sorry, George, but that's now how it works. Whether using the regular string-based Python paths or the new path module, a path *is* either absolute or relative, but cannot be both at the same time. This is therefore not an issue of representation but one of state. -Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Peter Hansen wrote:
Under Linux isn't it possible to open and read from directories much as
with files?
Not really, no.
Python 2.3.4 (#2, Jan 5 2005, 08:24:51)
[GCC 3.3.5 (Debian 1:3.3.5-5)] on linux2
Type help, copyright, credits or license for more information.
d = open('/usr/bin')
Traceback (most recent call last):
File stdin, line 1, in ?
IOError: [Errno 21] Is a directory
--
Robert Kern
[EMAIL PROTECTED]
In the fields of hell where the grass grows high
Are the graves of dreams allowed to die.
-- Richard Harter
--
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Re: Aliasing an object's __str__ to a different method
Thanks for all the additional replies thus far! Apparently the issue, as stated implicitly or explicitly by most of you, is that new-style class instances essentially defer their magic methods to the class's static versions of same. This is good to know :) Ironically, the reason I'm using new-style classes is that I only read up on them very recently, and was attempting to get myself into the habit of inheriting from 'object' by default. Go figure. Anyway, to take a step back, the *actual* actual reason for my investigation into this issue is that I'm attempting to create a collection of classes representing HTML page/form elements, many of which are represented differently depending on whether they're in a view or edit state. And ideally I wanted to be able to hold a collection of these objects and toggle them all to one state or the other, then bandy them about as if they were strings, e.g. mixing them with literal strings via str (obj). Clearly there are at least a handful of ways to accomplish this, but the one that came to mind first was, as I said at the beginning, to define both behaviors on each object and then have the ability to point __str__ to one or the other. I suppose now I need to figure out which is more important, that ease-of-use of overriding __str__ or whatever benefits new-style classes give (something I'm still a bit unclear on). Thanks again, Jeff -- Jeffrey E. Forcier Junior Developer, Research and Development Stroz Friedberg, LLC 15 Maiden Lane, 12th Floor New York, NY 10038 [main]212-981-6540 [direct]212-981-6546 http://www.strozllc.com This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No right to confidential or privileged treatment of this message is waived or lost by any error in transmission. If you have received this message in error, please immediately notify the sender by e-mail or by telephone at 212.981.6540, delete the message and all copies from your system and destroy any hard copies. You must not, directly or indirectly, use, disclose, distribute, print or copy any part of this message if you are not the intended recipient. -- http://mail.python.org/mailman/listinfo/python-list
Re: Using python to runother programs
this isn't really enough data to go on. What operating system (sounds like win2k/XP), does Crystal reports and unnamed accounting software have COM hooks? Look at Simon Brunning posts: http://www.brunningonline.net/simon/blog/archives/000652.html http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/279003 -- http://mail.python.org/mailman/listinfo/python-list
Lists pointers
Hello all,
I have written a simple whiteboard application. In my application, I
want to be able to set draw attributes. This part works. I have a
dictionary object which contains stuff like:
self.attr['Pen.Color'] = ...
self.attr['Pen.Thickness'] = ...
Now, the problem is that I want to be able to store attributes in a
list so they'll be easily accessed using the function keys. I.e. I have
the current attributes which I want to be able to store or retrieve
in/from a list,
The problem is that I have initialized the list like this:
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr)
I know what the problem is; they are all referencing the *same*
dictionary object. So, my question is: How do I initialize a list of
dictionary objects, where each list entry is its own object (which is a
copy from the self.drawAttr object).
Also, how do I store/restore entries to the list?
I have found the copy module, and it's copy method. I assume this
would work:
for i in range(0, 10):
self.storedAttr.append(copy.copy(self.drawAttr))
However, the concept of deep copy confuses me. Do I want it, or
don't I want it? I repeat: the attributes object is a simple dictionary.
Thankful for any advice.
--
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Re: [path-PEP] Path inherits from basestring again
Peter Hansen wrote:
Reinhold Birkenfeld wrote:
One thing is still different, though: a Path instance won't compare to a
regular
string.
Could you please expand on what this means? Are you referring to doing
and = type operations on Paths and strings, or == and != or all those
or something else entirely?
All of these. Do you need them?
Other minor differences, as requested on python-dev, are:
* size property - getsize() method.
* atime/mtime/ctime properties - atime()/mtime()/ctime() methods
What does this mean? The .size property and a getsize() method both
already exist (in my copy of path.py anyway) and do the same thing.
Same with the other ones mentioned above. Is someone working from an
out-of-date copy of path.py?
No. But the size of a file is somewhat volatile, and does not feel like
a property of the path to it. Remember: the path is not the file. Same
goes with the xtime() methods.
Different is the basename/directory/etc.: as long as the path stays the same,
these properties will stay the same.
* dirs() method - subdirs() method
Given that .files() exists, and returns a list of the files contained in
a path which represents a folder, why would one want to use subdirs()
instead of just dirs() to do the same operation for contained folders?
If subdirs() is preferred, then I suggest subfiles() as well. Otherwise
the change seems arbitrary and ill-conceived.
Well, I think that's right. Will change back to dirs().
* joinpath() method - added alias joinwith()
* splitall() method - parts() method
This reminds me of the *one* advantage I can think of for not
subclassing basestring, though it still doesn't make the difference in
my mind: strings already have split(), so Jason had to go with
splitpath() for the basic split operation to avoid a conflict. A
minor wart I guess.
At the moment, I think about overriding certain string methods that make
absolutely no sense on a path and raising an exception from them.
* Default constructor: Path() == Path(os.curdir)
To construct an empty path then one can still do Path('') ?
Yes.
* staticmethod Path.getcwd() - Path.cwd()
* bytes() / lines() / text() - read_file_{bytes,lines,text} methods
* write_{bytes,lines,text} - write_file_{bytes,lines,text} methods
Under Linux isn't it possible to open and read from directories much as
with files? If that's true, the above would seem to conflict with that
in some way. As with the the .subdirs() suggestion above, these changes
seem to me somewhat arbitrary. .bytes() and friends have felt quite
friendly in actual use, and I suspect .read_file_bytes() will feel quite
unwieldy. Not a show-stopper however.
It has even been suggested to throw them out, as they don't have so much to
do with a path per se. When the interface is too burdened, we'll have less
chance to be accepted. Renaming these makes clear that they are not operations
on the path, but on a file the path points to.
Phillip J. Eby suggested these to be set_file_xxx and get_file_xxx to
demonstrate
that they do not read or write a stream; how about that?
Reinhold
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Regarding Webbrowser Module in Python
Hi all, My query goes like this. I have two htm files.One is media_try_home.htm and the second one is media_try.htm.I am attaching these files to my mail so that you guys can understand the problem. Now, first simply open the media_try_home.htm and press PLAY THE FILE button.A video clip is opened.(Both the files should be in the same directory). Using webbrowser, I can first open the first file like this: webbrowser.open_new(c:\Myfolder\media_try_home.htm). But I want to play the second file directly using webbrowser but that doesn't work when I use the following : webbrowser.open_new (file:///c:\media_try.htm?start=60end=70location=mms%3A%2F%2Fedrul-develop.softeco.it%2F23%2F2004%2F12%2F23_20041218223000.wmvsubmit=PLAY+THE+FILE) If I simply paste this link in the browser, then it works direclty, bypassing the first file. May be it's due to the fact that file:/// is an ftp?Any ideas or clues what can I do to play the second file directly? Thanks in anticipation, Kamran Title: Documento senza titolo PLAY WINDOWS MEDIA FILE Start seconds End seconds Location Title: Documento senza titolo -- http://mail.python.org/mailman/listinfo/python-list
Re: Neat access to db query results
There's a few places to stash apps, libraries, or small code snippets so they can be search engined, if you provide some inline comments, unit/functional tests, and examples of how to use/known limitations: Vaults Parnassus, dmoz, ActiveState cookbook http://aspn.activestate.com/ASPN/Cookbook/Python http://www.pypackage.org/packages http://dmoz.org/Computers/Programming/Languages/Python/Modules/ http://www.vex.net/parnassus/ -- http://mail.python.org/mailman/listinfo/python-list
Re: What is your favorite Python web framework?
Hi, I have also been looking around to start web development. Almost everybody says - Zope h steep learning curve, so looking at alternatives. But to people have got past that curve. Is Zope worth it. My applications would be data entry heavy. Think inventory and accounting apps. Would going past the learning curve allow me to write applications like that. -- Dark Cowherd -- http://mail.python.org/mailman/listinfo/python-list
problem with property docstrings
I've observed something strange about property docstrings and I'm wondering if anyone here can clarify what's going on: if I create a class derived from property, the docstrings of the instances end up being that of the derived class, not the docstring passed into the property constructor. Example: class MyProp(property): MyProp docstring class Foo: p = MyProp(None, None, None, property p docstring) Foo.p.__doc__ 'MyProp docstring' Can anyone explain why this is? Is this a bug? -- http://mail.python.org/mailman/listinfo/python-list
Re: Lists pointers
Jan Danielsson wrote:
Hello all,
I have written a simple whiteboard application. In my application, I
want to be able to set draw attributes. This part works. I have a
dictionary object which contains stuff like:
self.attr['Pen.Color'] = ...
self.attr['Pen.Thickness'] = ...
Now, the problem is that I want to be able to store attributes in a
list so they'll be easily accessed using the function keys. I.e. I have
the current attributes which I want to be able to store or retrieve
in/from a list,
The problem is that I have initialized the list like this:
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr)
I know what the problem is; they are all referencing the *same*
dictionary object. So, my question is: How do I initialize a list of
dictionary objects, where each list entry is its own object (which is a
copy from the self.drawAttr object).
Also, how do I store/restore entries to the list?
I have found the copy module, and it's copy method. I assume this
would work:
for i in range(0, 10):
self.storedAttr.append(copy.copy(self.drawAttr))
However, the concept of deep copy confuses me. Do I want it, or
don't I want it? I repeat: the attributes object is a simple dictionary.
Thankful for any advice.
The easiest way to do it would be to create a new dictionary object for
each iteration of your loop. In this scenario, you would not need to
use the copy module.
In other words:
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append({ blah, blah, blah.. })
I hope this helps!
Regards,
Michael Loritsch
--
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Re: What is your favorite Python web framework?
Dark Cowherd wrote: My applications would be data entry heavy. Think inventory and accounting apps. Would going past the [Zope] learning curve allow me to write applications like that. You might want to look at Zope 3, there are several niceties for automatically (or semi-automatically if you prefer) generating input forms, validating them, applying the results to an object, etc. -- Benji York -- http://mail.python.org/mailman/listinfo/python-list
Re: unit test nested functions
[Andy] How can you unit test nested functions? Or do you have to pull them out to unit test them, which basically means I will never use nested functions. Several commons use cases (closures and factory functions) ultimately expose the inner function through the return value. If that is the case, the answer is simple, call the enclosing function and then run the test on the result. If the inner function never gets exposed, an argument could be made that you don't want to write a test for it -- that the inner function is just an implementation detail. This is black box testing and consistent with a test driven development approach. For whitebox testing, you could make an inner function visible by binding it to the enclosing function's attribute namespace. def f(x): def g(y): . . . f.g = g# make g visible as an attribute of f . . . Raymond -- http://mail.python.org/mailman/listinfo/python-list
Re: unit test nested functions
Raymond Hettinger wrote: [Andy] How can you unit test nested functions? For whitebox testing, you could make an inner function visible by binding it to the enclosing function's attribute namespace. def f(x): def g(y): . . . f.g = g# make g visible as an attribute of f . . . Note that when using this technique, f.g will not be bound until after you call the function: def f(x): ... def g(y): ... pass ... f.g = g ... f function f at 0xb7df3df4 f.g Traceback (most recent call last): File stdin, line 1, in ? AttributeError: 'function' object has no attribute 'g' f(1) f.g function g at 0xb7df3e2c -- Benji York -- http://mail.python.org/mailman/listinfo/python-list
Re: smtplib
On 7/19/05, Alberto Vera [EMAIL PROTECTED] wrote: Hello: Do you know If the smtplib routine have been changed in last releases? I used this script: http://docs.python.org/lib/SMTP-example.html but it didn't work with the last release. Do you know any idea about this change? Regards -- http://mail.python.org/mailman/listinfo/python-list If you are using Windows there is no SMTP server running on localhost by default so you may be getting an error. If you post the error you are getting it may help -- Dark Cowherd -- http://mail.python.org/mailman/listinfo/python-list
Friend wants to learn python
I have a friend who wants to learn python programming. I learned off the internet and have never used a book to learn it. What books do you recommend? Any suggestions would be appreciated. -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Reinhold Birkenfeld wrote:
Peter Hansen wrote (on Paths not allowing comparison with strings):
Could you please expand on what this means? Are you referring to doing
and = type operations on Paths and strings, or == and != or all those
or something else entirely?
All of these. Do you need them?
I believe so. If they are going to be basestring subclasses, why should
they be restricted in any particular way? I suppose that if you wanted
to compare a Path to a string, you could just wrap the string in a Path
first, but if the Path is already a basestring subclass, why make
someone jump through that particular hoop?
Other minor differences, as requested on python-dev, are:
* size property - getsize() method.
* atime/mtime/ctime properties - atime()/mtime()/ctime() methods
What does this mean? The .size property and a getsize() method both
already exist (in my copy of path.py anyway) and do the same thing.
Same with the other ones mentioned above. Is someone working from an
out-of-date copy of path.py?
No. But the size of a file is somewhat volatile, and does not feel like
a property of the path to it. Remember: the path is not the file. Same
goes with the xtime() methods.
Oh, so your original text was meant to imply that those properties *were
being removed*. That wasn't at all clear to me.
I understand the reasoning, but I'm unsure I agree with it. I fully
accept that the path is not the file, and yet I have a feeling this is a
pedanticism: most of the time when one is dealing with the _file_ one is
concerned with the content, and not much else. When one is dealing with
the _path_ one often wants to check the size, the modification time, and
so forth. For example, once one has the file open, one very rarely is
interested in when it was last modified.
In other words, I feel once again that Jason's original intuition here
was excellent, and that he chose practicality over purity in appropriate
ways, in a very Pythonic fashion. I confess to feeling that the
suggested changes are being proposed by those who have never actually
tried to put path.py to use in practical code, though I'm sure that's
not the case for everyone making those suggestions.
Still, once again this doesn't seem a critical issue to me and I'm happy
with either approach, if it means Path gets accepted in the stdlib.
At the moment, I think about overriding certain string methods that make
absolutely no sense on a path and raising an exception from them.
That would seem reasonable. It seems best to be very tolerant about
what makes no sense, though istitle() would surely be one of those to
go first. Also capitalize() (in spite of what Windows Explorer seems to
do sometimes), center(), expandtabs(), ljust(), rjust(), splitlines(),
title(), and zfill(). Hmm... maybe not zfill() actually. I could
imagine an actual (if rare) use for that.
.bytes() and friends have felt quite
friendly in actual use, and I suspect .read_file_bytes() will feel quite
unwieldy. Not a show-stopper however.
It has even been suggested to throw them out, as they don't have so much to
do with a path per se. When the interface is too burdened, we'll have less
chance to be accepted. Renaming these makes clear that they are not operations
on the path, but on a file the path points to.
Here again I would claim the practicality over purity argument. When
one has a Path, it is very frequently because one intends to open a file
object using it and do reads and writes (obviously). Also very often,
the type of reading and writing one wants to do is an all at once type
of thing, as those methods support. They're merely a convenience, to
save one doing the Path(xxx).open('rb').read thing when one can merely
do Path(xxx).bytes(), in much the same way that the whole justification
for Path() is that it bundles useful and commonly used operations
together into one place.
Phillip J. Eby suggested these to be set_file_xxx and get_file_xxx to
demonstrate
that they do not read or write a stream; how about that?
If they are there, they do exactly what they do, don't they? And they
do file.read() and file.write() operations, with slight nuances in the
mode passed to open() or the way the data is manipulated. Why would one
want to hide that, making it even harder to tie these operations
together with what is really going on under the covers? I think the
existing names, or at least ones with _read_ and _write_ in them
somewhere are better than set/get alternatives. It's just rare in
Python to encounter names quite as cumbersome as _write_file_bytes().
It might be good for those involved to discuss and agree on the
philosophy/principles behind using Path in the first place. If it's one
of pragmatism, then the arguments in favour of strictly differentiating
between path- and file- related operations should probably not be given
as much weight as those in favour of simple and convenient access
Re: list implementation
[sj] Thus, random access is an O(1) operation while insertion/deletion is an O(n) operation. [Raymond Hettinger] Yes. [Heikki Orsila aka host.invalid] Unfortunately no. Check Terry Reeds answer. Random access is O(1), insertion/deletion to front is O(n), and i/d to back is O(1). The back i/d operation has amortized O(1) cost. Duh. Excellent misreading of a simple answer to the OP's plain question. It is clear from his post that he already had a pretty accurate guess about how lists were implemented and the consequent performance implications. What was needed was a confirmation of his guess and a pointer to collections.deque() for O(1) insertion/deletion on the ends. For O(1) length changing ops in the middle, his suggestion of a linked list was not off base. IOW, a simple yes would have served. Raymond P.S. Non-standard abbreviations like, i/d, are rarely helpful to your readers. -- http://mail.python.org/mailman/listinfo/python-list
consistency: extending arrays vs. multiplication ?
Hi all, Just having started with python, I feel that simple array operations '*' and '+' don't do multiplication/addition but instead extend/join an array: a=[1,2,3] b=[4,5,6] a+b [1, 2, 3, 4, 5, 6] instead of what I would have expected: [5,7,9] or 2*a [1, 2, 3, 1, 2, 3] Well it is consistent to strings but tolerating string-operations to be special is ok to me as a + b - 'ab' :) Why not make it another function like a.stretch() or a.expand() and a.extend() is there doing the same anyway and is more readable... Putting this in a larger view: Ufuncs are very reasonable sin(a), etc ... all that won't work because of that '+','*' syntax. Ok I can use numarray for that, but seeing its PEP and a possible inclusion into python at some point that inconsistency is giving me quite some headache... Will that change in the future ? Or is this 100*[0] syntax put into stone for all ages ? Best, Soeren. PS: As I am very new to python please forgive/correct me! -- http://mail.python.org/mailman/listinfo/python-list
Re: Python vs. Access VBA
better to go with SQLite. Its cross platform and well proven. I think Firebird will give you that too, though I have never used it. Firebird is a great option, cross platform, it can work like access without any server running, using embedded mode to a full blown server which can handle terabytes of data. -- Dark Cowherd -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP on path module for standard library
Peter Hansen wrote: Just a note, though you probably know, that this is intended to be written this way with path: p / q path(u'a/b/c/d') I know, but it really doesn't look right to me. I think that my fundamental problem with all of this is that by making path a subclass of str/unicode it inherits inappropriate definitions of some common operations, most obviously addition, iteration and subscripting. These operations have obvious meaning for paths which is not the same as the meaning for string. Therefore (in my opinion) the two ought to be distinct. -- http://mail.python.org/mailman/listinfo/python-list
PostgreSQL Python vs PHP
Hi, I don't know anything about PHP and I'm initiating right now with PostgreSQL. Could someone tell me the pros and cons of assessing the PostgreSQL databases with Python vs. PHP? I will need to build a database that has to be assessed by a dozen clients via a web page in an intranet (possibly from outside, too). Is Python more used on the client side and PHP on the server side? I now Python, although I'm far from being an expert. Luis -- http://mail.python.org/mailman/listinfo/python-list
Re: unit test nested functions
[Andy] How can you unit test nested functions? [Raymond Hettinger] For whitebox testing, you could make an inner function visible by binding it to the enclosing function's attribute namespace. def f(x): def g(y): . . . f.g = g# make g visible as an attribute of f . . . [Benji York] Note that when using this technique, f.g will not be bound until after you call the function: That is a feature, not a bug. The inner function isn't even created until the outer function is run. def f(x): z = 30 def g(y): return 10 return 20 from dis import dis dis(f) 2 0 LOAD_CONST 1 (30) 3 STORE_FAST 1 (z) 3 6 LOAD_CONST 2 (code object g at 00A33660, file pyshell#37, line 3) 9 MAKE_FUNCTION0 12 STORE_FAST 2 (g) 5 15 LOAD_CONST 3 (20) 18 RETURN_VALUE The MAKE_FUNCTION step is where g comes into existence. That is a run-time operation, not compile time. If you are willing to be tricky, it is possible to write an accessor function that goes into f.func_code.co_consts, finds the code object whose co_name attribute is 'g', builds a wrapper function using types.FunctionType, and returns the result for unittesting. But that is not for the faint of heart ;-) Raymond -- http://mail.python.org/mailman/listinfo/python-list
Friend wants to learn python
I have a friend who wants to learn python programming. I learned off the internet and have never used a book to learn it. What books do you recommend? Any suggestions would be appreciated. -- http://mail.python.org/mailman/listinfo/python-list
How to realize ssh scp in Python
I would like to write a Python code like this:It can login a host by SSHafter login the host, use SCP to get a remote file, so it can deliver file to the host.then execute the programthen leave the hostFor example :STEP 1. ssh [EMAIL PROTECTED]STEP 2. Enter the password automatically STEP 3. run scp -r [EMAIL PROTECTED]:/home/xxx/program .STEP 4. Enter the password for SCP automatically STEP 5. run ./programSTEP 6. run exitI know telnetlib can help us with telnet, and how to deal with this SSH situation in Python?Thanks a lot for your help :) 需要一个2000兆的免费邮箱吗？网易免费邮箱是中国最多人使用的电子邮箱。 -- http://mail.python.org/mailman/listinfo/python-list
Re: Lists pointers
[EMAIL PROTECTED] wrote:
Jan Danielsson wrote:
Hello all,
I have written a simple whiteboard application. In my application, I
want to be able to set draw attributes. This part works. I have a
dictionary object which contains stuff like:
self.attr['Pen.Color'] = ...
self.attr['Pen.Thickness'] = ...
Now, the problem is that I want to be able to store attributes in a
list so they'll be easily accessed using the function keys. I.e. I have
the current attributes which I want to be able to store or retrieve
in/from a list,
The problem is that I have initialized the list like this:
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr)
I know what the problem is; they are all referencing the *same*
dictionary object. So, my question is: How do I initialize a list of
dictionary objects, where each list entry is its own object (which is a
copy from the self.drawAttr object).
Also, how do I store/restore entries to the list?
I have found the copy module, and it's copy method. I assume this
would work:
for i in range(0, 10):
self.storedAttr.append(copy.copy(self.drawAttr))
However, the concept of deep copy confuses me. Do I want it, or
don't I want it? I repeat: the attributes object is a simple dictionary.
Thankful for any advice.
The easiest way to do it would be to create a new dictionary object for
each iteration of your loop. In this scenario, you would not need to
use the copy module.
In other words:
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append({ blah, blah, blah.. })
And this would be equivalent to shallow copy. Whether you need a deep copy
depends on what each
blah is. More specifically it depends on whether the values of the dictionary
are mutable or not
(the keys are known to be immutable anyway). If they are immutable, a shallow
copy is enough. If
not, check whether all dictionaries refer to the same values or separate copies
of the values. Only
in the latter case you need deep copy.
HTH,
George
--
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Re: Friend wants to learn python
Maybe diveintopython.org can help -- http://mail.python.org/mailman/listinfo/python-list
How to realize ssh scp by Python
I would like to write a Python code like this:It can login a host by SSHafter login the host, use SCP to get a remote file, so it can deliver file to the host.then execute the programthen leave the hostFor example :STEP 1. ssh _yyy at 123.45.67.89STEP 2. Enter the password automatically STEP 3. run " scp -r zzz at 123.45.67.90:/home/xxx/program ."STEP 4. Enter the password for SCP automatically STEP 5. run "./program"STEP 6. run " exit"I know telnetlib can help us with telnet, and how to deal with this SSH situation in Python?Thanks a lot for your help :)__赶快注册雅虎超大容量免费邮箱?http://cn.mail.yahoo.com-- http://mail.python.org/mailman/listinfo/python-list
Re: time.time() under load between two machines
[EMAIL PROTECTED] writes: I am seeing negative latencies of up to 1 second. I am using ntp to synchronize both machines at an interval of 2 seconds, so the clocks should be very much in sync (and are from what I have observed). I agree that it is probably OS, perhaps I should hop over to a Microsoft newsgroup and pose the question, although I'm sure they will find a way to blame it on Python. We're getting off topic here, but what are the two machines ntp syncing to? Specifically, is one syncing to the other, or are they both syncing to the same external source, or - worst case - are they syncing to different external sources? Have you checked the drift file on the two machines? 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: PostgreSQL Python vs PHP
To be honest, this is a pretty open-ended question. Are there specific issues (SQL injection/security, minimizing db connections, simplest code, etc, your'e concerned with?) To be more honest, googline Python vs. PHP raises lots of hits http://wiki.w4py.org/pythonvsphp.html http://www.redcor.ch/wikis/semi_intern/BasicReferenceOfMoreLanguages -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Steven D'Aprano [EMAIL PROTECTED] writes: On Sat, 23 Jul 2005 11:48:27 +0300, Thanos Tsouanas wrote: Hello. I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. That looks rather confusing to me. Why not just call obj.bar, since it doesn't look like you are actually using the dictionary at all? Well, I needed exactly this functionality last week. I have a collection of (rather messy) classes that have a slew of attributes as values. I would have used a dictionary for this, but I didn't write the code. I have to be able to display these objects (in HTML, if it matters), and have as a requirement that the format string live in a database. My solution didn't look to different from dictobj. There's some extra mechanism to fetch the format string from the database, and some formatting of the attribute based on meta-information in the object, but it's the same basic idea. class dictobj(dict): class dictobj(dict): A dictionary d with an object attached to it, which treats d['foo'] as d.obj.foo. def __init__(self, obj): self.obj = obj def __getitem__(self, key): return self.obj.__getattribute__(key) I don't think this is particularly useful behaviour. How do you use it? def __str__(self): return self._format % self 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: PostgreSQL Python vs PHP
ok, to make this less open-ended, you should mention what O/S and web server you have in mind, whether the web and DB servers will be under your admin (big diff betw python and PHP, as far as finding shared server accounts at web hosts), what kinds of queries, concurrent read/write volumes, transactions, dirtiness, etc. etc Also if you build your questions to this newsgroup on past threads you've read, you will get absolute superb information, I guarantee it. -- http://mail.python.org/mailman/listinfo/python-list
Re: PostgreSQL Python vs PHP
gene tani wrote: To be honest, this is a pretty open-ended question. Are there specific issues (SQL injection/security, minimizing db connections, simplest code, etc, your'e concerned with?) Simplest code with be an important factor, since the db will be used far from max capabilities. Ease of use of the web page by clients is also a main factor. I need to build it from the server and also client side. For the client side I'll be using Python. But for the server side, I would like to hear some opinions. Is it worth learning Php? To be more honest, googline Python vs. PHP raises lots of hits http://wiki.w4py.org/pythonvsphp.html nice link :-) Thank you, Luis -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Peter Hansen [EMAIL PROTECTED] writes:
* staticmethod Path.getcwd() - Path.cwd()
* bytes() / lines() / text() - read_file_{bytes,lines,text} methods
* write_{bytes,lines,text} - write_file_{bytes,lines,text} methods
Under Linux isn't it possible to open and read from directories much
as with files?
The OS doesn't matter - python won't let you open a directory as a
file, even if the underlying OS will. The comment in
Objects/fileobject.c is:
/* On Unix, fopen will succeed for directories.
In Python, there should be no file objects referring to
directories, so we need a check. */
I think - but I'm not positive, and don't have a Linux box handy to
check on - that this comment is false if your Unix is really Linux.
mike
--
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Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.
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Re: unit test nested functions
Raymond Hettinger wrote: [Benji York] Note that when using this technique, f.g will not be bound until after you call the function: That is a feature, not a bug. The inner function isn't even created until the outer function is run. I'm fully aware of that. I just didn't want the OP get bit by it. -- Benji York -- http://mail.python.org/mailman/listinfo/python-list
Re: PostgreSQL Python vs PHP
gene tani wrote: ok, to make this less open-ended, you should mention what O/S and web server you have in mind, whether the web and DB servers will be under your admin (big diff betw python and PHP, as far as finding shared server accounts at web hosts), what kinds of queries, concurrent read/write volumes, transactions, dirtiness, etc. etc Also if you build your questions to this newsgroup on past threads you've read, you will get absolute superb information, I guarantee it. I'll be using Apache, under Linux. The db server will be under my admin. A dozen clients acessing the db. For the first project: Three or four of them will be using queries mainly from three tables with: table 1: 350 lines x 20 cols table 2: 350 lines x 6 cols table 3: 4200 lines x 5 cols as an estimate. Other clients will be very light users but need easy web interface for mouse clicks only. Thank you for your support and excuse me for my ignorance, but I'm starting the project and would like to start it in the right direction. Luis -- http://mail.python.org/mailman/listinfo/python-list
Re: Copying attributes
On Thu, 21 Jul 2005 00:45:12 +0200, red [EMAIL PROTECTED] wrote:
Hi,
I'm writing a script for Blender and need to build a face array. My
engine needs that all faces must be triangles, so I convert quads to
triangles by dividing them into two triangles. Here is the function:
def build_face_table(mesh):
face_table = {}
# face_table = [] ??
Irrelevant nit: Why a dict? You seem to be building it with all the keys as
integers of xrange(last_i),
in which case appending a face_table list to build it and later accessing
face_table[key]
will go faster than your current dict. OTOH, if you will be deleting various
elements later,
your dict may be best.
i = 0
for f in mesh.faces:
if len(f.v) == 3: # triangle
face_table[i] = f
# face_table.append(f) # no need for i counting
i += 1
elif len(f.v) == 4: # quad
f1 = NMesh.Face()
f2 = NMesh.Face()
f1.mat = f.mat
## f1.normal = copy.deepcopy(f.normal)
f1.normal = NMesh.Vert(f.normal[0], f.normal[1],
f.normal[2])
f is a quad at this point, right? So unless the quad is restricted to a plane,
it couldn't
have a normal in general. Could that be it? BTW, if it is not a plane, one
choice of diagonal
may be better than the other in getting two triangles that fit the underlying
3D surface best.
If there is a normal, why wouldn't ft.normal = f.normal[::] work?
Is normal more than a 3-tuple or list to record unit vector components in some
coordinate system?
f1.v.append(f.v[0])
f1.v.append(f.v[1])
f1.v.append(f.v[2])
Why append, and is there restricted property magic behind f1.v so that plain old
f1.v = f.v[:3]
wouldn't work?
# or f1.v = [f.v[0], f.v[1], f.v[2]] if you want to be
consistent with f2 below
f2.mat = f.mat
# f2.normal = ?? # could this face be picked up later
indirectly and cause the missing normal exception?
f2.v.append(f.v[2])
f2.v.append(f.v[3])
f2.v.append(f.v[0])
Why appends? Does f2.v ever grow beyond 3 items? E.g.,
f2.v = [f.v[2], f.v[3], f.v[0]] # are quad vertices
listed clockwise or ccw and
# are triangles in a
sequence totally independent, or
# is there some
systematic vertex sharing in the order
# that something might
depend on, or benefit optimization-wise from?
face_table[i] = f1
#face_table.append(f1) ??
i += 1
face_table[i] = f2
#face_table.append(f2) ??
i += 1
else:
message = Can't build face from 2 vertices.
Why is len(f.v)4 not just a 3D surface point cluster,
in which case it might
be possible to find an internal point to slice
radiating triangles from. E.g.,
imagine an almost-plane small pentagon on a large
sphere, and slice from its center
to each peripheral pair of vertices to make triangles.
Draw.PupMenu(Face Table Error%t|+message)
return
return face_table
# do you need it as a dict? Unless you modify it, a list will get you
# the same elements as your dict by writing face_table[some_index]
If you need to iterate and have both index key and value, you can use your dict
like
for i, face in sorted(face_table.items()): # leave out sorted call if
order does not matter
# ...
or use the more efficient list version of face_table like
for i, face in enumerate(facetable): # will naturally be in sort order
# ...
Everything seems be ok, but i'm getting:
Traceback (most recent call last):
File string, line 169, in write
File string, line 102, in build_face_table
AttributeError: normal
I was wondering why? Though the face has an attribute called normal!
Just simply test:
nv = f.normal
and it works! But why my new faces (f1 and f2) no?
Did it work on a quad face? What about putting in a debug print before places
you use
f.normal, e.g.
assert hasattr(f, 'normal'), 'This f\n\n%r\n\ndid not have a
normal attribute!!' % f
If f.repr doesn't give you enough info, you can format something better in the
assert message string.
Greetings.
--
_red _ __ _
BTW, I don't know Blender at all, just reading between the lines ;-)
Hope I triggered a useful
Re: Lists pointers
Jan Danielsson wrote:
Hello all,
I have written a simple whiteboard application. In my application, I
want to be able to set draw attributes. This part works. I have a
dictionary object which contains stuff like:
self.attr['Pen.Color'] = ...
self.attr['Pen.Thickness'] = ...
Now, the problem is that I want to be able to store attributes in a
list so they'll be easily accessed using the function keys. I.e. I have
the current attributes which I want to be able to store or retrieve
in/from a list,
The problem is that I have initialized the list like this:
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr)
I know what the problem is; they are all referencing the *same*
dictionary object. So, my question is: How do I initialize a list of
dictionary objects, where each list entry is its own object (which is a
copy from the self.drawAttr object).
Hi Jan son of Daniel,
you might initialize self.storedAttr with empty dicts and fill them
later:
self.soredAttr = [{}]*10
for entry in self.storedAttr:
entry.update(self.drawAttr)
Also, how do I store/restore entries to the list?
I have found the copy module, and it's copy method. I assume this
would work:
for i in range(0, 10):
self.storedAttr.append(copy.copy(self.drawAttr))
However, the concept of deep copy confuses me. Do I want it, or
don't I want it? I repeat: the attributes object is a simple dictionary.
Thankful for any advice.
A *shallow copy* creates a new dictionary and copies the references, a
*deep copy* tries to create a new reference for each existing object in
the dict. The disadvantage of deepcopy is that it does not work in many
cases:
copy.deepcopy([lambda :None])
Traceback (most recent call last):
...
TypeError: function() takes at least 2 arguments (0 given)
As the docs tell:
This version does not copy types like module, class, function, method,
stack trace, stack frame, file, socket, window, array, or any similar
types.
I wonder if one couldn't pickle a module and reimport it in order to
create a copy of it ;)
IMO this is a weakness of the algorithm. One usually doesn't want to
duplicate a function so that a new reference of a function is not
needed because it is readonly and the algorithm could reuse the same
reference. For classes I don't if the assertion in the docs is actually
true?
class A:pass
copy.deepcopy(A)
class __main__.A at 0x01191990
class A(object):
... def __init__(self):pass
...
copy.deepcopy(A)
class '__main__.A'
Regards,
Kay
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Re: consistency: extending arrays vs. multiplication ?
Soeren Sonnenburg wrote: Hi all, Just having started with python, I feel that simple array operations '*' and '+' don't do multiplication/addition but instead extend/join an array: a=[1,2,3] This isn't an array. It is a list. If you want an array, use Numeric/numarray. If you want lists, use lists. Lists will never grow the kind of behavior you're asking for. -- Robert Kern [EMAIL PROTECTED] In the fields of hell where the grass grows high Are the graves of dreams allowed to die. -- Richard Harter -- http://mail.python.org/mailman/listinfo/python-list
Re: Friend wants to learn python
EnderLocke wrote: I have a friend who wants to learn python programming. I learned off the internet and have never used a book to learn it. What books do you recommend? Any suggestions would be appreciated. I recommend Learning Python 2nd Edition by Mark Lutz David Ascher (O'Reilly) its reasonable easy to read no heavy language, but clear concept and examples. It does not require any previous programming experience, although being comfortable with computer terms and knowing some basic concepts of programming does make you read faster through the book. My overall conclusion was that the authors know what they are talking about and are honest in what they want to achieve. When done with that the reader has enough experience to at least know where to go further to learn more about python. -- mph -- http://mail.python.org/mailman/listinfo/python-list
How can I get an sha1 hash in base32?
I know how to make a hash(using mhash), but instead of encoded as hex I want it in base32 for use with the bitzi catalog. python-bitzi is useful but way too slow for just getting the hash of a file(am going to use it elsewhere). Thanks. Elmo -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Peter Hansen wrote:
Reinhold Birkenfeld wrote:
Peter Hansen wrote (on Paths not allowing comparison with strings):
Could you please expand on what this means? Are you referring to doing
and = type operations on Paths and strings, or == and != or all those
or something else entirely?
All of these. Do you need them?
I believe so. If they are going to be basestring subclasses, why should
they be restricted in any particular way? I suppose that if you wanted
to compare a Path to a string, you could just wrap the string in a Path
first, but if the Path is already a basestring subclass, why make
someone jump through that particular hoop?
Do you have a use case for the comparison? Paths should be compared only
with other paths.
Other minor differences, as requested on python-dev, are:
* size property - getsize() method.
* atime/mtime/ctime properties - atime()/mtime()/ctime() methods
What does this mean? The .size property and a getsize() method both
already exist (in my copy of path.py anyway) and do the same thing.
Same with the other ones mentioned above. Is someone working from an
out-of-date copy of path.py?
No. But the size of a file is somewhat volatile, and does not feel like
a property of the path to it. Remember: the path is not the file. Same
goes with the xtime() methods.
Oh, so your original text was meant to imply that those properties *were
being removed*. That wasn't at all clear to me.
I understand the reasoning, but I'm unsure I agree with it. I fully
accept that the path is not the file, and yet I have a feeling this is a
pedanticism: most of the time when one is dealing with the _file_ one is
concerned with the content, and not much else. When one is dealing with
the _path_ one often wants to check the size, the modification time, and
so forth. For example, once one has the file open, one very rarely is
interested in when it was last modified.
My line of thought is that a path may, but does not need to refer to an
existing, metadata-readable file. For this, I think a property is not
proper.
In other words, I feel once again that Jason's original intuition here
was excellent, and that he chose practicality over purity in appropriate
ways, in a very Pythonic fashion. I confess to feeling that the
suggested changes are being proposed by those who have never actually
tried to put path.py to use in practical code, though I'm sure that's
not the case for everyone making those suggestions.
Still, once again this doesn't seem a critical issue to me and I'm happy
with either approach, if it means Path gets accepted in the stdlib.
At the moment, I think about overriding certain string methods that make
absolutely no sense on a path and raising an exception from them.
That would seem reasonable. It seems best to be very tolerant about
what makes no sense, though istitle() would surely be one of those to
go first. Also capitalize() (in spite of what Windows Explorer seems to
do sometimes), center(), expandtabs(), ljust(), rjust(), splitlines(),
title(), and zfill(). Hmm... maybe not zfill() actually. I could
imagine an actual (if rare) use for that.
I'll look into it. What about iteration and indexing? Should it support
for element in path or for char in path or nothing?
.bytes() and friends have felt quite
friendly in actual use, and I suspect .read_file_bytes() will feel quite
unwieldy. Not a show-stopper however.
It has even been suggested to throw them out, as they don't have so much to
do with a path per se. When the interface is too burdened, we'll have less
chance to be accepted. Renaming these makes clear that they are not
operations
on the path, but on a file the path points to.
Here again I would claim the practicality over purity argument. When
one has a Path, it is very frequently because one intends to open a file
object using it and do reads and writes (obviously). Also very often,
the type of reading and writing one wants to do is an all at once type
of thing, as those methods support. They're merely a convenience, to
save one doing the Path(xxx).open('rb').read thing when one can merely
do Path(xxx).bytes(), in much the same way that the whole justification
for Path() is that it bundles useful and commonly used operations
together into one place.
Phillip J. Eby suggested these to be set_file_xxx and get_file_xxx to
demonstrate
that they do not read or write a stream; how about that?
If they are there, they do exactly what they do, don't they? And they
do file.read() and file.write() operations, with slight nuances in the
mode passed to open() or the way the data is manipulated. Why would one
want to hide that, making it even harder to tie these operations
together with what is really going on under the covers? I think the
existing names, or at least ones with _read_ and _write_ in them
somewhere are better than set/get alternatives.
Re: Lists pointers
* Kay Schluehr wrote:
you might initialize self.storedAttr with empty dicts and fill them
later:
self.soredAttr = [{}]*10
for entry in self.storedAttr:
entry.update(self.drawAttr)
As a matter of fact, you're doing the same ;-)
In [1]: x = [{}] * 10
In [2]: x[0]['a'] = 1
In [3]: x[1]['b'] = 2
In [4]: x
Out[4]:
[{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2},
{'a': 1, 'b': 2}]
nd
--
Umfassendes Werk (auch fuer Umsteiger vom Apache 1.3)
-- aus einer Rezension
http://pub.perlig.de/books.html#apache2
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Re: How can I get an sha1 hash in base32?
In [EMAIL PROTECTED], Elmo Mäntynen wrote: I know how to make a hash(using mhash), but instead of encoded as hex I want it in base32 for use with the bitzi catalog. python-bitzi is useful but way too slow for just getting the hash of a file(am going to use it elsewhere). Thanks. Doesn't Bitzi calculate some kind of audio fingerprint? Just a hash of the file would result in very different hash values for different codecs, bitrates etc. for the same audio data. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: consistency: extending arrays vs. multiplication ?
In [EMAIL PROTECTED], Soeren Sonnenburg wrote: Just having started with python, I feel that simple array operations '*' and '+' don't do multiplication/addition but instead extend/join an array: a=[1,2,3] b=[4,5,6] a+b [1, 2, 3, 4, 5, 6] Both operate on the lists themselves and not on their contents. Quite consistent if you ask me. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: PEP on path module for standard library
On Sat, 23 Jul 2005 07:05:05 +1000, John Machin [EMAIL PROTECTED] wrote: Daniel Dittmar wrote: Duncan Booth wrote: I would have expected a path object to be a sequence of path elements rather than a sequence of characters. Maybe it's nitpicking, but I don't think that a path object should be a 'sequence of path elements' in an iterator context. This means that for element in pathobject: has no intuitive meaning for me, so it shouldn't be allowed. Try this: A file-system is a maze of twisty little passages, all alike. Junction == directory. Cul-de-sac == file. Fortunately it is signposted. You are dropped off at one of the entrance points (current directory, say). You are given a route (a path) to your destination. The route consists of a list of intermediate destinations. for element in pathobject: follow_sign_post_to(element) Exception-handling strategy: Don't forget to pack a big ball of string. Anecdotal evidence is that breadcrumbs are unreliable. indulging what=my penchant for seeking the general behind the specific ;-) ISTM a path is essentially a representation of a script whose interpretation by an orderly choice of interpreters finally leads to accessing to some entity, typically a serial data representation, through an object, perhaps a local proxy, that has standard methods for accessing the utimate object's desired info. IOW, a path sequence is like a script text that has been .splitline()'d and and the whole sequence fed to a local interpreter, which might chew through multiple lines on its own, or might invoke interpreters on another network to deal with the rest of the script, or might use local interpreters for various different kinds of access (e.g., after seeing 'c:' vs 'http://' vs '/c' vs '//c' etc. on the platform defining the interpretation of the head element). Turning a single path string into a complete sequence of elements is not generally possible unless you have local knowledge of the syntax of the entire tail beyond the the prefix you have to deal with. Therefore, a local platform-dependent Pathobject class should, I think, only recognize prefixes that it knows how to process or delegate processing for, leaving the interpretation of the tail to the next Pathobject instance, however selected and/or located. So say (this is just a sketch, mind ;-) po = Pathobject(string representation of whole path) results in a po that splits out (perhaps by regex) a prefix, a first separator/delimiter, and the remaining tail. E.g., in class Pathobject, def __init__(self, pathstring=None) if pathstring is None: #do useful default?? self.pathstring = pathstring self.prefix, self.sep, self.tail = self.splitter(pathstring) if self.prefix in self.registered_prefixes: self.child = self.registered_prefixes[self.prefix](self.tail) else: self.child = [] self.opened_obj = None Then the loop inside a local pathobject's open method po.open() might go something like def open(self, *mode, **kw): if self.child: self.opened_obj = self.child.open(self.tail, *mode, **kw) else: self.opened_obj = file(self.pathstring, *mode) return self And closing would just go to the immediately apparent opened object, and if that had complex closing to do, it would be its responsibility to deal with itself and its child-derived objects. def close(self): self.opened_object.close() The point is that a given pathobject could produce a new or modified pathobject child which might be parsing urls instead of windows file system path strings or could yield an access object producing something entirely synthetic. A synthetic capability could easily be introduced if the local element pathobject instance looked for e.g., 'synthetic://' as a possible first element (prefix) string representation, and then passed the tail to a subclass defining synthetic:// path interpretation. E.g., 'synthetic://temp_free_diskspace' could be a platform-independent way to get such info as that. Opening 'testdata:// ...' might be an interesting way to feed test suites, if pathobject subclasses could be registered locally and found via the head element's string representation.' One point from this is that a path string represents an ordered sequence of elements, but is heterogenous, and therefore has potentially heterogenous syntax reflected in string tails with syntax that should be interpreted differently from the prefix syntax. Each successive element of a path string effectively requires an interpreter for that stage of access pursuit, and the chain of processing may result in different path entities/objects/representations on different systems, with different interpretations going on, sharing only that they are part of the process of getting access to something and providing access services, if it's not a one-shot access.
Re: Getting a dictionary from an object
On Sat, Jul 23, 2005 at 11:22:21PM +1000, Steven D'Aprano wrote: On Sat, 23 Jul 2005 11:48:27 +0300, Thanos Tsouanas wrote: Hello. I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. That looks rather confusing to me. Why not just call obj.bar, since it doesn't look like you are actually using the dictionary at all? [...] I don't think this is particularly useful behaviour. How do you use it? print foo %do where do is a dictobj object... -- Thanos Tsouanas .: My Music: http://www.thanostsouanas.com/ http://thanos.sians.org/ .: Sians Music: http://www.sians.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: PyGTK or wxPython (not a flame war) on Windows
Hello! How well does PyGTK run on Windows (98, 2K, XP)? How stable is it? Will I be able to make an executable (using Py2Exe) of an application that uses PyGTK? I _do_ like PyGTK on Windows. It works without problems. You can find a ready to use py2exe script on http://www.pythonwiki.de/PyGtk. You could also bundle the runtime DLLs with your py2exe'd application, but I have never done this. You could try doing this like described here: http://aspn.activestate.com/ASPN/Mail/Message/py2exe-users/2476686 (use the setup.py script from the wiki and start at (2) in the mail). HTH. greets, Marek PS: Yes, I admit it is harder than py2exe + wxPython but I still like PyGTK. -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Reinhold Birkenfeld [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] I'll look into it. What about iteration and indexing? Should it support for element in path or for char in path or nothing? I frankly can't think of a use for iterating over the characters in the path, but I have a number of programs that check elements, iterate over them and index them (frequently backwards). I also like to know the number of elements, which seems to make sense as len(path). Again, the number of characters in the path seems to be utterly useless information - at least, I can't imagine a use for it. John Roth Reinhold -- http://mail.python.org/mailman/listinfo/python-list
Re: dictionary that discards old items
On 21 Jul 2005 19:29:32 -0700, Raymond Hettinger [EMAIL PROTECTED] wrote:
[Will McGugan]
I need a collection class that behaves like a dictionary but when it
reaches 'n' items it discards the oldest item so that the length never
goes above 'n'. (Its for caching search results)
import collections
class Cache(dict):
def __init__(self, n, *args, **kwds):
self.n = n
self.queue = collections.deque()
dict.__init__(self, *args, **kwds)
def __setitem__(self, k, v):
self.queue.append(k)
dict.__setitem__(self, k, v)
if len(self) self.n:
oldk = self.queue.popleft()
del self[oldk]
# . . .
# make similar modifications to setdefault, __delitem__, fromkeys
# and other mutating methods as needed
# Example
c = Cache(3)
for w in 'the quick brown fox jumped over the lazy dog'.split():
c[w] = w[:1].upper()
print repr(c)
Minor comment: There is a potential name collision problem for keyword
n=something,
so what is considered best practice to avoid that? __n or such as the n arg?
def foo(n, *args, **kw): print n, args, kw
...
foo(1)
1 () {}
foo(n=5)
5 () {}
foo(3, n=5)
Traceback (most recent call last):
File stdin, line 1, in ?
TypeError: foo() got multiple values for keyword argument 'n'
Regards,
Bengt Richter
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Re: wxPython - DB Form generator unit
On 7/19/05, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Is anyone know about a DB form generator unit under wxPython ? What that's means ? I add information about a Query, or a ListOfDict, I set some other infos (Lookups, others), and it is generate a Form with edit boxes, listboxes, etc. Then I can fill up the form with a record's datas. User can modify them. After I can call Apply method, and every modifications are stored in a result. You should look into Dabo. It is a framework for creating database apps, and comes with a wizard that lets you create an app that queries, updates, edits, adds and deletes records in a variety of databases. What database are you using? # p.d. -- http://mail.python.org/mailman/listinfo/python-list
Re: return None
Grant Edwards wrote: Personally, I don't really like the idea that falling off the botton of a function implicitly returns None. It's just not explicit enough for me. My preference would be that if the function didn't execute a return statement, then it didn't return anyting and attempting to use a return value would be an error. This is a bad idea. Classically, distinguishing between functions that return things and functions that don't return things explicitly divides the callable object space. From my CS101 class with its incredibly exciting dive into the world of useless pseudocode, callables that returned things were called 'functions' and callables that didn't were called 'procedures'. Some languages do make this distinction; QBASIC, for example, had 'gosub' separate from function calls. What do you do for an early break from a function that still returns not-even-None [ReallyNone], return? That looks and acts like a 'real' return statement, and the distinction between return-without-a-value-so-maybe-except and return-with-a-value is suddenly magnified to real importance. Further, and I consider this a truly damning case, look at decorater. A naive logging decorator could be defined like this: def logger(func): def new_func(*args, **kwargs): print '%s called with:' % func.__name__, args, kwargs retval = func(*args,**kwargs) print '%s returns:', retval return retval return new_func This logger works without modification for both value and non-value returning functions. Its output isn't quite as pretty for non-value functions, but it works and the implementation is both simple and flexible. With a function-schism, to keep its simple implementation 'logger' would have to be rewritten as 'flogger' (same as current-logger, for use on functions), and 'plogger' (for use on procedures). The downside here is that if the function/method changed to or from a procedure, the decorator would have to be switched. Alternatively, the logger decorator could be longer and explicitly catch the possible exception. But why should we have to write like that, for a use-case that doesn't even represent a true error -- arguably not even an exceptional case? Python's definitely not a BD language, talk of floggers aside. -- http://mail.python.org/mailman/listinfo/python-list
Re: Aliasing an object's __str__ to a different method
Paolino wrote: Little less ugly: In [12]:class A(object): : def __str__(self):return self.__str__() : def str(self):return 'ciao' : def setStr(self):self.__str__=self.str : In [13]:a=A() In [14]:a.setStr() In [15]:str(a) Out[15]:'ciao' Not quite bug-free, by my eye that'll infintely recur if you call str(A()). -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting a dictionary from an object
Thanos Tsouanas wrote: I would like to have a quick way to create dicts from object, so that a call to foo['bar'] would return obj.bar. The following works, but I would prefer to use a built-in way if one exists. Is there one? Maybe I'm not understanding your problem, but have you looked at the builtin vars()? STeVe -- http://mail.python.org/mailman/listinfo/python-list
Re: PostgreSQL Python vs PHP
Luis P. Mendes wrote: I need to build it from the server and also client side. For the client side I'll be using Python. But for the server side, I would like to hear some opinions. Is it worth learning Php? If you know Python and don't know PHP, there's little benefit from spending the time learning it. But, PHP is extremely simple to work with and you can produce results VERY quickly. Part of the reason is that it's already intended to be a web-embedded language and doesn't reqire additonal frameworks, libraries or configuration like Python does. One thing that botheres me when using Python in php-like way is that the indentation is significant property becomes a nuisance when you intertwine HTML and code (which you shouldn't be doing anyway ;) ). The benefit of Python is that is a much cleaner language with well defined interfaces and you'll probably maintain a large application easier if it's in Python. There are no significant performance differences, and no really significant differences in programming approach. -- http://mail.python.org/mailman/listinfo/python-list
Re: Copying attributes
On Sat, 23 Jul 2005 18:30:29 GMT, [EMAIL PROTECTED] (Bengt Richter) wrote: [...] Did it work on a quad face? What about putting in a debug print before places you use f.normal, e.g. assert hasattr(f, 'normal'), 'This f\n\n%r\n\ndid not have a normal attribute!!' % f If f.repr doesn't give you enough info, you can format something better in the assert message string. f.__repr__ was what I meant (as called due to %r in format), sorry. Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
Re: is this possible?
On Saturday 23 July 2005 03:26 am, Steven D'Aprano wrote: On Fri, 22 Jul 2005 07:59:42 -0700, scrimp wrote: As others have suggested, if you have to deal with PDF files without Acrobat, you could use ghostscript. Also pre-installed on many versions of Linux, and probably other Unixes as well, is pdf2ps which will convert the PDF file to a pure postscript file, which you can then print to any printer which understands postscript. IIRC, pdf2ps is a utility that comes with Ghostscript, and actually does use it to do the transformation (that is, I think it's just a script to run ghostscript with the appropriate options). -- Terry Hancock ( hancock at anansispaceworks.com ) Anansi Spaceworks http://www.anansispaceworks.com -- http://mail.python.org/mailman/listinfo/python-list
Re: dictionary that discards old items
[Raymond Hettinger] class Cache(dict): def __init__(self, n, *args, **kwds): self.n = n self.queue = collections.deque() dict.__init__(self, *args, **kwds) [Bengt Richter] Minor comment: There is a potential name collision problem for keyword n=something, so what is considered best practice to avoid that? __n or such as the n arg? I don't know what best practice is, but if you want to guarantee to avoid the name collision, you can write: def __init__(*args, **kwargs): self = args[0] self.n = args[1] self.queue = collections.deque() dict.__init__(self, *args[2:], **kwargs) It's not pretty though. ;) STeVe -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
On Sat, 23 Jul 2005 23:26:19 +1000, John Machin wrote: Steven D'Aprano wrote: ''.join(map(lambda n: chr(n), (0x73, 0x70, 0x61, 0x6D))) 'spam' Why the verbal diarrhoea? One line is hardly verbal diarrhoea. What's wrong with the (already posted) ''.join(map(chr, (0x73, 0x70, 0x61, 0x6D))) ??? Nothing. If I had seen the already posted solution using chr on its own without lambda, I wouldn't have bothered posting the lambda solution. But I didn't, so I did. As another poster has already pointed out, lambda cries out for over-use, and this was a perfect example of it. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: tuple to string?
On Sat, 23 Jul 2005 23:31:04 +1000, John Machin wrote: You don't need the sissy parentheses; '%c' * len(t) % t works just fine :-) Ah, ok. Didn't want to lookup the precedence rules... Look up the precedence rules? Are you aware of any language where * / and % _don't_ have the same precedence?? Do languages like Pascal that don't have string formatting expressions, or use the % operator, count? How about languages like Forth that don't have precedence rules at all, unless first come, first served is a precedence rule? I'm not being academic here. I have used both these languages extensively, admittedly many years ago. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: [path-PEP] Path inherits from basestring again
Reinhold Birkenfeld wrote:
[on comparing Paths and stings]
Do you have a use case for the comparison? Paths should be compared only
with other paths.
I can think of lots, though I don't know that I've used any in my
existing (somewhat limited) code that uses Path, but they all involve
cases where I would expect, if comparisons were disallowed, to just wrap
the string in a Path first, even though to me that seems like it should
be an unnecessary step:
if mypath.splitpath()[0] == 'c:/temp':
if 'tests' in mypath.dirs():
and lots of other uses which start by treating a Path as a string
first, such as by doing .endswith('_unit.py')
Any of these could be resolved by ensuring both are Paths, but then I'm
not sure there's much justification left for using a baseclass of
basestring in the first place:
if mypath.splitpath()[0] == Path('c:/temp'):
if Path('tests') in mypath.dirs():
Question: would this latter one actually work? Would this check items
in the list using comparison or identity? Identity would simply be
wrong here.
[on removing properties in favour of methods for volatile data]
My line of thought is that a path may, but does not need to refer to an
existing, metadata-readable file. For this, I think a property is not
proper.
Fair enough, though in either case an attempt to access that information
leads to the same exception. I can't make a strong argument in favour
of properties (nor against them, really).
What about iteration and indexing? Should it support
for element in path or for char in path or nothing?
As John Roth suggests, the former seems a much more useful thing to do.
The latter is probably as rarely needed as it is with regular strings
(which I believe is roughly never in Python).
[on .read_file_bytes() etc]
I think it is not exactly bad that these names are somehow outstanding,
as that demonstrates that something complex and special happens.
Point taken. What about ditching the file part, since it is redundant
and obvious that a file is in fact what is being accessed. Thus:
.read_bytes(), .read_text(), .write_lines() etc.
-Peter
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Re: return None
Christopher Subich wrote: print '%s returns:', retval Not that it matters, but this line should be: print '%s returns:' % func.__name__, retval -- http://mail.python.org/mailman/listinfo/python-list
what's wrong with my code using subprocess?
I decide to seperate my data collection routine from my data analysis and storage program to a seperate process, so I try to use the new subprocess model in Python 2.4. The main program spawns the subprocess and receives data from the pipe. When some event occurs (e.g. the user clicks the 'Stop' button on GUI), the main program will send the subprocess a command to change its behavior or ask it to exit. However, my code (attached below) doesn't work. Under Linux, the output is: output waiting subprocess exit Traceback (most recent call last): File receiver.py, line 19, in ? main() File receiver.py, line 13, in main print p.stdin, 'exit' IOError: [Errno 32] Broken pipe /output And Under Windows XP, p.wait() never returns: output waiting subprocess exit [hanging here] /output What's wrong? # collector.py import threading class Main(object): def __init__(self): self.keep_going = True self.t = threading.Thread(target=self.work) self.t.start() cmd = raw_input() while cmd != 'exit': cmd = raw_input() self.keep_going = False self.t.join() def work(self): while self.keep_going: print '$' * 82 if __name__ == '__main__': Main() # receiver.py (the main program) from subprocess import Popen, PIPE def main(): p = Popen(['python', 'collector.py'], stdout=PIPE, stdin=PIPE) count = 0 for line in p.stdout: data = line.strip() # process(data) count += 1 if count = 1000: print p.stdin, 'exit' print 'waiting subprocess exit' p.wait() if __name__ == '__main__': main() -- Qiangning Hong I'm usually annoyed by IDEs because, for instance, they don't use VIM as an editor. Since I'm hooked to that, all IDEs I've used so far have failed to impress me. -- Sybren Stuvel @ c.l.python Get Firefox! http://www.spreadfirefox.com/?q=affiliatesamp;id=67907amp;t=1 -- http://mail.python.org/mailman/listinfo/python-list
Re: Lists pointers
On Sat, 23 Jul 2005 17:03:08 +0200, Jan Danielsson wrote:
The problem is that I have initialized the list like this:
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr)
I know what the problem is; they are all referencing the *same*
dictionary object. So, my question is: How do I initialize a list of
dictionary objects, where each list entry is its own object (which is a
copy from the self.drawAttr object).
self.drawAttr = { blah, blah, blah.. }
self.storedAttr = [ ]
for i in range(0, 10):
self.storedAttr.append(self.drawAttr.copy())
You only need to worry about the difference between copy and deepcopy if
the objects inside the dict are complex objects like dicts and lists.
You also said that: I want to be able to store attributes in a list so
they'll be easily accessed using the function keys.
I don't think this is good usage. What happens when you change the
attributes in one place but forget to change it in the other?
A better solution would be to set up either a list or a mapping from
function key to attribute, rather than to a COPY of the attribute. Why
change things in two places rather than one?
Something like this:
# set up attributes before hand
self.attr['Pen.Color'] = 'blue'
self.attr['Pen.Thickness'] = 1
self.attr['Pen.State'] = 'down'
# etc
# now point the function keys to attributes
self.functionkeys = {'F1' = 'Pen.Color', 'F2' = 'Pen.Thickness',
'F3' = 'Pen.State', ... }
Then, when you want to access the current value of some attribute, instead
of looking up a list:
# bad way
def get_attribute(fkey):
if fkey = 'F1':
return self.storedAttr[0]
elif fkey = 'F2':
return self.storedAttr[1]
...
elif fkey = 'F12':
return self.storedAttr[11]
you would do something like this:
# good way
def get_attribute(fkey):
return self.attr[self.functionkeys[fkey]]
Also, how do I store/restore entries to the list?
That question is awfully open-ended. Can you be more specific?
I have found the copy module, and it's copy method. I assume this
would work:
for i in range(0, 10):
self.storedAttr.append(copy.copy(self.drawAttr))
However, the concept of deep copy confuses me. Do I want it, or
don't I want it? I repeat: the attributes object is a simple dictionary.
That depends on what is inside your simple dictionary. For immutable
objects like ints, floats and strings, copy is sufficient:
D1 = {1: 'hello', 2: 'there'}
D1
{1: 'hello', 2: 'there'}
D2 = D1.copy()
D1[1] = 'go'
D1
{1: 'go', 2: 'there'}
D2
{1: 'hello', 2: 'there'}
See what happens when the values are mutable objects:
DM1 = {1: [0,1], 2: [4, 5]}
DM2 = DM1.copy()
DM1[3] = [0,2]
DM1
{1: [0, 1], 2: [4, 5], 3: [0, 2]}
DM2
{1: [0, 1], 2: [4, 5]}
So far so good. But now look:
DM1[1].append(999)
DM1
{1: [0, 1, 999], 2: [4, 5], 3: [0, 2]}
DM2
{1: [0, 1, 999], 2: [4, 5]}
The difference is that although copy makes a copy of the top level of the
dict, it DOESN'T make copies of the individual objects within the dict.
This doesn't matter is the objects are immutable, but if they are lists or
other dicts, you can get surprises like the above.
--
Steven.
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