Announce: Pyevolve 0.5 released !

[Perone]

The Pyevolve v.0.5 was released.

Pyevolve was developed to be a complete genetic algorithms framework
written in pure python.

More information at: http://pyevolve.sourceforge.net


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Re: Why GIL? (was Re: what's the point of rpython?)

[Carl Banks]

On Jan 23, 11:45 pm, Bryan Olson fakeaddr...@nowhere.org wrote:
 Carl Banks wrote:
  Classes in Python are mutable types, usually.  Class instances are
  (except for the refcount) immutable objects, usually.

 There's where we disagree. I assert that class instances are usually
 mutable objects.

Nope, you're dead wrong, nothing more to it.  The bits of a class
instance never change.  The __dict__ is a mutable object.  The class
instance itself isn't.  It's not reasonable to call an object whose
bits can't change a mutable obect.

Anyway, all you're doing is distracting attention from my claim that
instance objects wouldn't need to be locked.  They wouldn't, no matter
how mutable you insist these objects whose bits would never change
are.


  BTW, here's a minor brain bender: immutable types are mutable objects.

 Some brains are too easily bent.
[Snip attempt to take this comment seriously]

And some brains are so stodgy they can't even take a lighthearted
comment lightheartedly.


Carl Banks
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Re: Two import questions in Python 3.0

[Gabriel Genellina]

En Sat, 24 Jan 2009 05:24:15 -0200, Kay Schluehr kay.schlu...@gmx.net  
escribió:



1. I'd expected that absolute imports are used in Python 3.0 by
default. I may be wrong. I've written two versions of a module
sucks.py

sucks.py
-
print (import from lib.sucks)

sucks.py
-
print (import from package.sucks)

The first is placed in the lib directory that is globally visible by
means of PYTHONPATH. The second one is placed in a package

package/
 __init__.py
 sucks.py
 A.py

The package also contains a module A.py defined by

A.py
--
import sucks

Running A yields import from package.sucks which means unconditional
relative import. It shadows the globally visible sucks.py module. I've
expected it the other way round.


If you run A.py as a script, it does not know it lives inside a package.  
You must *import* A for it to become aware of the package.
Also, the directory containing the script comes earlier than PYTHONPATH  
entries in sys.path -- so watch for that case too.



python test_parser.py
Traceback (most recent call last):
File test_parser.py, line 12, in module
   from . import support
ValueError: Attempted relative import in non-package

The standard error of the years to come that makes working with Python
harder and reminds me that it is not a scripting language anymore
because you can't run anything as a script not even a test.


I always consider that packages are libraries. Application code uses a  
library (by importing things from it). Test code should mimic closely that  
behavior: my tests always import the package, like the application would  
do.


Anyway I should revisit the strategy, I've not evaluated yet how much is  
affected by absolute imports and other changes in 3.0


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Re: Why GIL?

[Hrvoje Niksic]

Carl Banks pavlovevide...@gmail.com writes:

 On Jan 23, 11:45 pm, Bryan Olson fakeaddr...@nowhere.org wrote:
 Carl Banks wrote:
  Classes in Python are mutable types, usually.  Class instances are
  (except for the refcount) immutable objects, usually.

 There's where we disagree. I assert that class instances are usually
 mutable objects.

 Nope, you're dead wrong, nothing more to it.  The bits of a class
 instance never change.  The __dict__ is a mutable object.  The class
 instance itself isn't.  It's not reasonable to call an object whose
 bits can't change a mutable obect.

The bits of class instances can very well change.

 class X(object): pass
...
 x = X()
 d = x.__dict__
 x.__dict__ = {}
 map(id, [d, x.__dict__])
[170329876, 170330012]

The Python cookbook even describes patterns that depend on this
operation working.  Class instance's contents can also change if
__slots__ is in use, when its __class__ is assigned to (admittedly the
latter being a rare operation, but still).

 Anyway, all you're doing is distracting attention from my claim that
 instance objects wouldn't need to be locked.  They wouldn't, no
 matter how mutable you insist these objects whose bits would never
 change are.

Only if you're not implementing Python, but another language that
doesn't support __slots__ and assignment to instance.__dict__.
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Re: Why GIL? (was Re: what's the point of rpython?)

[Gabriel Genellina]

En Sat, 24 Jan 2009 06:06:02 -0200, Carl Banks pavlovevide...@gmail.com  
escribió:

On Jan 23, 11:45 pm, Bryan Olson fakeaddr...@nowhere.org wrote:

Carl Banks wrote:
 Classes in Python are mutable types, usually.  Class instances are
 (except for the refcount) immutable objects, usually.

There's where we disagree. I assert that class instances are usually
mutable objects.


Nope, you're dead wrong, nothing more to it.  The bits of a class
instance never change.  The __dict__ is a mutable object.  The class
instance itself isn't.  It's not reasonable to call an object whose
bits can't change a mutable obect.

Anyway, all you're doing is distracting attention from my claim that
instance objects wouldn't need to be locked.  They wouldn't, no matter
how mutable you insist these objects whose bits would never change
are.


Me too, I don't get what you mean. Consider a list instance, it contains a  
count of allocated elements, and a pointer to some memory block. They  
change when the list is resized. This counts as mutable to me. I really  
don't understand your claim.


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Re: Stalled ticket in Python bug tracker

[Peter Otten]

Steven D'Aprano wrote:

 I'm interested in this ticket in the bug tracker:
 
 http://bugs.python.org/issue2527
 
 but it seems to have been stalled for nine months. Is there a procedure
 for starting it up again? Should I ask about it on the python-dev mailing
 list, or just wait until somebody happens to notice it?
 
 Peter Otten, if you're reading this, is your offer to jump through the
 necessary hoops still standing?

I guess what killed any chance for the patch to be included was that there
was a competing patch that I asked to be reversed. Also, just saying that
you are willing to provide docs and test didn't work either.

What's needed then as a 'sine qua non' is an updated patch against the tip
with documentation and tests.

If you don't beat me to it I may give it another try, but probably not
before next month.

Peter
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Re: Why GIL?

[Paul Rubin]

Hrvoje Niksic hnik...@xemacs.org writes:
 Not only registered at the beginning of the function, but also (since
 CPython uses C, not C++) explicitly unregistered at every point of
 exit from the function.  Emacs implements these as macros called GCPRO
 and UNGCPRO, and they're very easy to get wrong.  In a way, they are
 even worse than the current Python INCREF/DECREF.

That's a fairly natural style in Lisp implementation and it is not
that difficult to code in.  I've hacked inside Emacs and have written
another interpreter with a similar setup; it's certainly easier than
keeping track of refcounts in my experience.  For one thing, you can
raise exceptions anywhere you want, and the stack unwind can clean up
the gc protection, but it can't know nearly as easily which refcounts
to adjust, unless you record all the increfs the same way as the
GCPROs.
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Web authentication urllib2

[Gabriel]

Hello,

I'm new in Python and i would like to write script which need to login 
to a website. I'm experimenting with urllib2,

especially with something like this:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(username='user', password='pass'))
f = opener.open('https://web.com', params)
data = f.read()
f.close()

And the problem is, that this code logs me in on some sites, but on 
others doesn't, especially on the one I really
need to login. And i don't know why. So is there some way how to debug 
this code and find out why that script cannot

login on that specific site?

Sorry if this question is too lame, but i am really beginner both in 
python and web programming .)


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Re: strange error whilst porting to 2.6

[Steve Holden]

Benjamin Peterson wrote:
 Robin Becker robin at NOSPAMreportlab.com writes:
 Well that's not really acceptable as a solution is it? :)
 
 This doesn't happen in Python 3.0,
 so you could port to that. :)
 
 In 2.7, the better recursion depth
 handling
 in Py3k may be backported,but the
 best you can do for now is not touch
 the recursion limit or just shut
 the error up.
 
Perhaps an interim solution would implement an error message more
helpful in ensuring the exception not be raised? This is currently a bit
like Your code is wrong: strictly correct, and totally unhelpful.

regards
 Steve
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Re: Relax Syntax for Augmented Arithmetic?

[Steve Holden]

Aahz wrote:
 In article mailman.7801.1232715276.3487.python-l...@python.org,
 Steve Holden  st...@holdenweb.com wrote:
 I understand what you are saying, but if the id() associated with a name
 doesn't change after augmented assignment it seems a little wrong-headed
 to argue that the augmented assignment always binds a new value to the
 name.

 What you are actually saying is that it's up to the method that
 implements the augmented assignment whether the same (mutated) object or
 a different one is returned, right? And that the left-hand side of the
 assignment is always bound to the result of that method.
 
 That's overall more correct, but I wanted to emphasize that there is
 *always* a binding operation being performed.  Whether what gets bound to
 the target is a new object or an existing object is up to the augmented
 assignment method.

nods

Yes, we're on the same page. Maybe I was being too pedantic ...

regards
 Steve
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Re: var is None vs. var == None

[Steve Holden]

Steven D'Aprano wrote:
 On Fri, 23 Jan 2009 20:33:45 -0500, Steve Holden wrote:
 
 Steven D'Aprano wrote:
 On Fri, 23 Jan 2009 14:58:34 -0500, Gerald Britton wrote:

 Hi -- Some time ago I ran across a comment recommending using var is
 None instead of var == None (also var is not None, etc.)
 That entirely depends on whether you wish to test for something which
 *is* None or something with *equals* None. Those two things have
 different meanings.

 No they don't, because the language *guarantees* the None object is a
 singleton, so anything that *equals* None *is* None.
 
 Twice in one day. Have they put funny chemicals in the water over there? 
 *wink*
 
Nope, but you know what newsgroup response propagation is like ...

 Steve, in case you missed my earlier response:
 
 class Empty:
 ... def __eq__(self, other):
 ... return not bool(other)
 ...
 e = Empty()
 e == None
 True
 e is None
 False
 
 
 An instance that compares equal to anything false doesn't strike me as 
 particularly bizarre or pathological. For instance, the Python Cookbook 
 has an implementation for the Null object pattern. The implementation 
 given compares unequal to everything, but suggests defining an 
 appropriate __eq__ if you need different behaviour.
 
Sure, my syllogism was not strictly true, hence my final quote:

 Of course there can be pathological objects with bizarre comparison
 methods. And the is test helps avoid them.

Personally I believe that the Empty class is at least slightly pathological.

regards
 Steve
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Re: Two import questions in Python 3.0

[Kay Schluehr]

On 24 Jan., 09:21, Gabriel Genellina gagsl-...@yahoo.com.ar wrote:

 If you run A.py as a script, it does not know it lives inside a package.
 You must *import* A for it to become aware of the package.
 Also, the directory containing the script comes earlier than PYTHONPATH
 entries in sys.path -- so watch for that case too.

Thanks, yes. I always make the same error thinking that a directory
with the ritual __init__ file is actually a package ( as some kind of
platonic entity ), something that is more obvious to me than it is to
the runtime. The relative import semantics introduced with Python 2.5
has made the error just visible that was hidden to me for about a
decade. Shit.
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Re: strange error whilst porting to 2.6

[Robin Becker]

Steve Holden wrote:

Benjamin Peterson wrote:

Robin Becker robin at NOSPAMreportlab.com writes:

Well that's not really acceptable as a solution is it? :)

This doesn't happen in Python 3.0,
so you could port to that. :)


my initial attempts in this direction were even less successful :(




Perhaps an interim solution would implement an error message more
helpful in ensuring the exception not be raised? This is currently a bit
like Your code is wrong: strictly correct, and totally unhelpful.



well after wrapping all the calls to isinstance I think I have found the 
 particular call and args that are causing the problem, but I still 
don't really understand why the problem is occurring.

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Re: Web authentication urllib2

[Gabriel Genellina]

En Sat, 24 Jan 2009 06:52:57 -0200, Gabriel dun...@dreams.sk escribió:

I'm new in Python and i would like to write script which need to login  
to a website. I'm experimenting with urllib2,

especially with something like this:

 opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
 urllib2.install_opener(opener)

 params = urllib.urlencode(dict(username='user', password='pass'))
 f = opener.open('https://web.com', params)
 data = f.read()
 f.close()

And the problem is, that this code logs me in on some sites, but on  
others doesn't, especially on the one I really
need to login. And i don't know why. So is there some way how to debug  
this code and find out why that script cannot

login on that specific site?


Start by looking at the web page that you normally use to log into the  
site; probably the form contains more fields than just username and  
password.
In some cases it may be necesary to use ethereal (or any protocol  
analizer), to see exactly what is actually transmitted when you log in  
using your browser. Later you may try to reproduce the same thing with  
Python.


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Re: Why GIL? (was Re: what's the point of rpython?)

[Steve Holden]

Carl Banks wrote:
 On Jan 23, 8:22 pm, Bryan Olson fakeaddr...@nowhere.org wrote:
 Paul Rubin wrote:
 Bryan Olson writes:
 BTW, class instances are usually immutable and thus don't require a
 mutex in the system I described.
 Then you are describing a language radically different from Python.
 That one threw me for a minute too, but I think the idea is that the
 class instance itself is immutable, while its slots (specifically the
 attribute dictionary) point to mutable objects.
 The meaning of 'immutable' is well-established in the Python literature.
 Python's immutable types include tuple, frozenset, and various kinds of
 numbers and strings. Class instances, not so much.
 
 Of course class instances aren't immutable types: they're not even
 types.  Let me suggest that there is a distinction between an
 immutable type and an immutable object.
 
 Immutable types are what you are talking about: it means that the type
 provides usable mutator methods.  (Whether they mutate the object
 itself or some associated object doesn't matter.)  Immutable objects
 are a different thing: it means the object cannot change in memory.
 
 Classes in Python are mutable types, usually.  Class instances are
 (except for the refcount) immutable objects, usually.
 
 We usually talk about mutability of types, but mutability of objects
 is appropriate for discussion as well.  So I can't really agree with
 your assessment that I wrong to call class instances immutable objects
 aside from refcounts.
 
 BTW, here's a minor brain bender: immutable types are mutable objects.
 
 
 What's more, this matters when considering a GIL-less implementation.
 Typical method calls can traverse lots of mutable stuff just to find the
 function to invoke.
 
 Now that doesn't make sense at all.  What is all this mutable stuff
 you have to go through, and what does it have to do with the GIL-less
 implementation?  Can you explain further?  Or are you just saying
 it'll be slow.
 
OK, so we have recently discussed whether objects are values, whether
function arguments are passed by reference, whether names are
references, and now we are, I suspect, about to have a huge further
discussion on the meaning of immutable.

Sometimes I start to find this eternal pedantry a little tedious. I
suspect it's time I once more dropped out of c.l.py for a while.

regards
 Steve
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Re: Web authentication urllib2

[Steve Holden]

Gabriel wrote:
 Hello,
 
 I'm new in Python and i would like to write script which need to login
 to a website. I'm experimenting with urllib2,
 especially with something like this:
 
 opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
 urllib2.install_opener(opener)
 
 params = urllib.urlencode(dict(username='user', password='pass'))
 f = opener.open('https://web.com', params)
 data = f.read()
 f.close()
 
 And the problem is, that this code logs me in on some sites, but on
 others doesn't, especially on the one I really
 need to login. And i don't know why. So is there some way how to debug
 this code and find out why that script cannot
 login on that specific site?
 
 Sorry if this question is too lame, but i am really beginner both in
 python and web programming .)
 
That's actually pretty good code for a newcomer! There are a couple of
issues you may be running into.

First, not all sites use application-based authentication - they may
use HTTP authentication of some kind instead. In that case you have to
pass the username and password as a part of the HTTP headers. Michael
Foord has done a fair write-up of the issues at

  http://www.voidspace.org.uk/python/articles/authentication.shtml

and you will do well to read that if, indeed, you need to do basic
authentication.

Second, if it *is* the web application that's doing the authentication
in the sites that are failing (in other words if the credentials are
passed in a web form) then your code may need adjusting to use other
field names, or to include other data as required by the login form. You
can usually find out what's required by reading the HTML source of the
page that contains the login form.

Thirdly [nobody expects the Spanish Inquisition ...], it may be that
some sites are extraordinarily sensitive to programmed login attempts
(possible due to spam), typically using a check of the Agent: HTTP
header to make sure that the login attempt is coming from a browser
and not a program. For sites like these you may need to emulate a
browser response more fully.

You can use a program like Wireshark to analyze the network traffic,
though you can get add-ons for Firefox that will show you the HTTP
headers on request and response.

regards
 Steve
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Re: The First Law Of comp.lang.python Dynamics

[Hendrik van Rooyen]

 Martin P. Hellwig martin.hell...@dcuktec.org wrote:

 Or you can argue that even when an argument is repeated indefinitely it 
 doesn't make it suddenly right.

This is no good.
It's a well known fact that anything I tell you three times is true.

To demonstrate:

Tim Rowe's post earlier in this thread was the funniest one in a long time.
Tim Rowe's post earlier in this thread was the funniest one in a long time.
Tim Rowe's post earlier in this thread was the funniest one in a long time.

see - it's true!

- Hendrik


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Re: Does Python really follow its philosophy of Readability counts?

[Steven D'Aprano]

On Fri, 23 Jan 2009 21:36:59 -0500, Luis Zarrabeitia wrote:

 Quoting Steven D'Aprano st...@remove-this-cybersource.com.au:
 
 On Fri, 23 Jan 2009 13:07:55 -0500, Luis Zarrabeitia wrote:
 
  It should be in _our_ power as the team of all participant coders on
  _our_ project to decide if we should mess with the internals or not.
  
  What makes no sense is that it should be in the original author's
  power to decide, if he is not part of _our_ team.
 
 Makes *no* sense? There's *no* good reason *at all* for the original
 author to hide or protect internals?
 
 My bad, sorry.
 It makes sense... if the original author is an egotist who believes he
 must control how I use that library.

Then I guess Guido must be such an egotist, because there's plenty of 
internals in Python that you can't (easy) mess with.


 Or, if external forces make him do
 it (maybe like, 'oh, if I change python, then I'm not using python
 anymore').

That parenthesised comment makes no sense to me. Python has changed 
significantly since it was first released. Recently, print became a 
function instead of a statement, and one of the motivations for this was 
to allow people to change the behaviour of Python's print simply by 
defining a new function. Shadowing built-ins, as they call it, is a 
feature, not a bug. I can't see any good reason for thinking that if you 
change (say) the way Python prints, you don't have Python any more.

Even more fundamental changes have occurred, e.g. new style classes, 
ABCs, nested scopes.


[...]
 If a variable is marked as... I don't like 'private', I'll call it
 'implementation detail', I would not use it without good reason. Not
 even by subclassing it. Why do you assume that I'd change list._length
 if I could? I wouldn't.

I didn't say you would change it on a whim. I said that *if* it were 
exposed to Python code, you *could* change it. You might change it 
because you thought you had a good reason to. You might change it by 
accident. You might not realise the consequences of changing it. Who 
knows? It doesn't matter what your motives are.

My point is that you claimed that there is no good reason at all for 
hiding implementation details. Python is full of implementation details 
which are quite effectively hidden from Python programmers. So there are 
two possibilities:

(1) you are right that it makes no sense (your words) for the original 
author (in this case, Guido) to hide those implementation details from 
Python programmers; or

(2) you are wrong that it makes no sense, because there is at least one 
case where the original author (Guido again) did a sensible thing by 
hiding implementation details.

In an effort to avoid going round and round in circles, let me explicitly 
say that option (2) does not imply that it always makes sense to hide 
implementation details.



 Anyway, did you notice that your counter-example was a radical
 change-the-way-python-works scenario? 

No, my scenario is merely extending what you can already do with pure-
Python classes to built-in classes written in C. It would have a radical 
effect (pure Python code could core dump easily) but it wouldn't be a 
radical change. It might take as little as one new function.


[...]
 So what you're saying is that the fundamental design of Python -- to be
 a high-level  language that manages memory for you while avoiding
 common programming errors such as buffer overflows -- makes no sense.
 Is that what you intended?
 
 Yes, that's what I intended, obviously. I'd like to have buffer
 overflows in python. In case you don't understand irony: don't go
 putting words in my mouth. I'm not putting words in yours.

And neither am I. I'm pointing out the logical implications of your 
position. If you find those implications unpleasant, then perhaps you 
should modify your position to be less extreme and more realistic.


 As I see it, you have two coherent positions. On the one hand, you
 could be like Mark Wooding, and say that Yes you want to risk buffer
 overflows by messing with the internals -- in which case I'm not sure
 what you see in Python, which protects so many internals from you. Or
 you can say that you made a mistake, that there are *some* good reasons
 to protect/hide internals from external access.
 
 Or, I could have a third option: assume that I am a grownup who knows
 what he is doing.

This is totally orthogonal to what we're discussing. Whether you are a 
grownup or a child, whether you have good reasons or bad reasons, you can 
still make either of the two choices.


 After all, even with all those protections in list,
 I could just create an extension module to shoot me in the foot anyway,
 if I really wanted to.

Yes you could, and you could hack the OS to manipulate data behind the 
scenes, and you could build a hardware device to inject whatever data you 
want directly into the memory. You can do any of those things. So what?

Data hiding isn't about some sort of mythical 100% certainty against 

Re: About SCons Re: progress: compiling python2.5 under msys (specifically but not exclusively under wine) with msvcr80

[anatoly techtonik]

On Sat, Jan 24, 2009 at 12:28 AM, Roumen Petrov

 I would better use SCons for both unix and windows builds. In case of
 windows for both compilers - mingw and microsoft ones. To port curses
 extension to windows I need to know what gcc options mean, what are
 the rules to write Makefiles and how to repeat these rules as well as
 find options in visual studio interface. Not mentioning various
 platform-specific defines and warning fixes.

 Did you select one of existing curses library for windows ?

I've selected PDCurses and successfully compiled the module and run
demos manually - you may see the batch and the patch at
http://bugs.python.org/issue2889

However, I was asked for VS2008 project file and this is where it all
stopped for 8 months already. First I couldn't get the VS2008, then it
refused to run on my W2K and now I can't get enough time to learn it
(including that I have 50%/40% experience in PHP/Python and only 5%/5%
C/Java).

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Re: Web authentication urllib2

[Gabriel]

First, thank you both

I think this isn't basic auth, because this page has form login.
I read site's html source and used wireshark to analyze communication 
between my browser and website and i really find out that a was ignoring 
one field


I added it to the parameters but it didn't help..
Maybe i'm still missing something

Here's the post packet:
http://student.fiit.stuba.sk/~sevecek06/auth.txt

and here's the code again, with little change and real web location added:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(login='login', pwd='pass', page=''))
f = opener.open('https://www.orangeportal.sk/', params)
data = f.read()
f.close()

Login and pass are fake ofc.

Thank you in advice for any help.


Steve Holden wrote:

Gabriel wrote:

Hello,

I'm new in Python and i would like to write script which need to login
to a website. I'm experimenting with urllib2,
especially with something like this:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(username='user', password='pass'))
f = opener.open('https://web.com', params)
data = f.read()
f.close()

And the problem is, that this code logs me in on some sites, but on
others doesn't, especially on the one I really
need to login. And i don't know why. So is there some way how to debug
this code and find out why that script cannot
login on that specific site?

Sorry if this question is too lame, but i am really beginner both in
python and web programming .)


That's actually pretty good code for a newcomer! There are a couple of
issues you may be running into.

First, not all sites use application-based authentication - they may
use HTTP authentication of some kind instead. In that case you have to
pass the username and password as a part of the HTTP headers. Michael
Foord has done a fair write-up of the issues at

  http://www.voidspace.org.uk/python/articles/authentication.shtml

and you will do well to read that if, indeed, you need to do basic
authentication.

Second, if it *is* the web application that's doing the authentication
in the sites that are failing (in other words if the credentials are
passed in a web form) then your code may need adjusting to use other
field names, or to include other data as required by the login form. You
can usually find out what's required by reading the HTML source of the
page that contains the login form.

Thirdly [nobody expects the Spanish Inquisition ...], it may be that
some sites are extraordinarily sensitive to programmed login attempts
(possible due to spam), typically using a check of the Agent: HTTP
header to make sure that the login attempt is coming from a browser
and not a program. For sites like these you may need to emulate a
browser response more fully.

You can use a program like Wireshark to analyze the network traffic,
though you can get add-ons for Firefox that will show you the HTTP
headers on request and response.

regards
 Steve


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Re: Web authentication urllib2

[Gabriel]

Oh, nevermind, it's working.
Thanks

Gabriel wrote:

First, thank you both

I think this isn't basic auth, because this page has form login.
I read site's html source and used wireshark to analyze communication 
between my browser and website and i really find out that a was ignoring 
one field


I added it to the parameters but it didn't help..
Maybe i'm still missing something

Here's the post packet:
http://student.fiit.stuba.sk/~sevecek06/auth.txt

and here's the code again, with little change and real web location added:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(login='login', pwd='pass', page=''))
f = opener.open('https://www.orangeportal.sk/', params)
data = f.read()
f.close()

Login and pass are fake ofc.

Thank you in advice for any help.


Steve Holden wrote:

Gabriel wrote:

Hello,

I'm new in Python and i would like to write script which need to login
to a website. I'm experimenting with urllib2,
especially with something like this:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(username='user', password='pass'))
f = opener.open('https://web.com', params)
data = f.read()
f.close()

And the problem is, that this code logs me in on some sites, but on
others doesn't, especially on the one I really
need to login. And i don't know why. So is there some way how to debug
this code and find out why that script cannot
login on that specific site?

Sorry if this question is too lame, but i am really beginner both in
python and web programming .)


That's actually pretty good code for a newcomer! There are a couple of
issues you may be running into.

First, not all sites use application-based authentication - they may
use HTTP authentication of some kind instead. In that case you have to
pass the username and password as a part of the HTTP headers. Michael
Foord has done a fair write-up of the issues at

  http://www.voidspace.org.uk/python/articles/authentication.shtml

and you will do well to read that if, indeed, you need to do basic
authentication.

Second, if it *is* the web application that's doing the authentication
in the sites that are failing (in other words if the credentials are
passed in a web form) then your code may need adjusting to use other
field names, or to include other data as required by the login form. You
can usually find out what's required by reading the HTML source of the
page that contains the login form.

Thirdly [nobody expects the Spanish Inquisition ...], it may be that
some sites are extraordinarily sensitive to programmed login attempts
(possible due to spam), typically using a check of the Agent: HTTP
header to make sure that the login attempt is coming from a browser
and not a program. For sites like these you may need to emulate a
browser response more fully.

You can use a program like Wireshark to analyze the network traffic,
though you can get add-ons for Firefox that will show you the HTTP
headers on request and response.

regards
 Steve


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Re: A java hobbyist programmer learning python

[TheFlyingDutchman]

On Jan 23, 8:57 am, Dennis Lee Bieber wlfr...@ix.netcom.com wrote:
 On Fri, 23 Jan 2009 01:48:32 -0800 (PST), TheFlyingDutchman
 zzbba...@aol.com declaimed the following in comp.lang.python:

  abstraction. In Python, all class attributes are public but names may
  be mangled to discourage unauthorized access, but otherwise not
  prevented. It is up to the designer to provide the appropriate
  interfaces to the data so that the client programmer does not have to
  resort to manipulating the encapsulated data attributes.

         Double underscore mangling was not implemented to discourage
 unauthorized access. Its primary purpose is to prevent name space
 conflicts when an extended subclass and its parent class use the same
 name for an attribute, but that attribute is not of the same meaning.
 Using the __ prefix means BOTH attributes are part of the instance, but
 the subclass only see's its variant and should make calls into
 superclass methods to modify the parent variant.

         Python convention is that a single underscore -- which does NOT
 perform name mangling -- is the indicator meant to discourage
 unauthorized access.


Is there a significant performance hit with using the double
underscore for signifying a variable you want to be private? It seems
like it is advantageous that someone trying for direct access has to
use a different notation, which will help to emphasize that it
shouldn't be access directly.

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Re: Web authentication urllib2

[Steve Holden]

Gabriel wrote:
 First, thank you both
 
 I think this isn't basic auth, because this page has form login.
 I read site's html source and used wireshark to analyze communication
 between my browser and website and i really find out that a was ignoring
 one field
 
 I added it to the parameters but it didn't help..
 Maybe i'm still missing something
 
 Here's the post packet:
 http://student.fiit.stuba.sk/~sevecek06/auth.txt
 
 and here's the code again, with little change and real web location added:
 
 opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
 urllib2.install_opener(opener)
 
 params = urllib.urlencode(dict(login='login', pwd='pass', page=''))
 f = opener.open('https://www.orangeportal.sk/', params)
 data = f.read()
 f.close()
 
If you look at the login form on the home page of that portal you will see

form name=form_login action=/portal/do_login.dwp method=POST

This means that the form should be submitted to

  https://www.orangeportal.sk/portal/do_login.dwp

Some forms submit to the same URL that contain them, but many don't.
This is one of the ones that requires submission to a different URL!

regards
 Steve
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Porting 3.0 to 2.6 - from __future__ import super missing?

[andrew cooke]

Hi,

I have some 3.0 code, which I would like to make work with 2.6.
However, there does not seem to be support for the new super() (no
args) via __future__.  Is that correct?  If so, what's the best way to
handle this?

Thanks,
Andrew
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Re: Web authentication urllib2

[Gabriel]

Yep, i realize this a minute after posting, sorry.

And thank you again .)

Steve Holden wrote:

Gabriel wrote:

First, thank you both

I think this isn't basic auth, because this page has form login.
I read site's html source and used wireshark to analyze communication
between my browser and website and i really find out that a was ignoring
one field

I added it to the parameters but it didn't help..
Maybe i'm still missing something

Here's the post packet:
http://student.fiit.stuba.sk/~sevecek06/auth.txt

and here's the code again, with little change and real web location added:

opener = urllib2.build_opener(urllib2.HTTPCookieProcessor())
urllib2.install_opener(opener)

params = urllib.urlencode(dict(login='login', pwd='pass', page=''))
f = opener.open('https://www.orangeportal.sk/', params)
data = f.read()
f.close()


If you look at the login form on the home page of that portal you will see

form name=form_login action=/portal/do_login.dwp method=POST

This means that the form should be submitted to

  https://www.orangeportal.sk/portal/do_login.dwp

Some forms submit to the same URL that contain them, but many don't.
This is one of the ones that requires submission to a different URL!

regards
 Steve


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What's the business with the asterisk?

[mk]

Hello everyone,

From time to time I spot an asterisk (*) used in the Python code 
_outside_ the usual *args or **kwargs application.


E.g. here: http://www.norvig.com/python-lisp.html

def transpose (m):
  return zip(*m)
 transpose([[1,2,3], [4,5,6]])
[(1, 4), (2, 5), (3, 6)]

What does *m mean in this example and how does it do the magic here?

Regards,
mk


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Re: What's the business with the asterisk?

[Tim Chase]

 From time to time I spot an asterisk (*) used in the Python code 
_outside_ the usual *args or **kwargs application.


E.g. here: http://www.norvig.com/python-lisp.html

def transpose (m):
   return zip(*m)
  transpose([[1,2,3], [4,5,6]])
[(1, 4), (2, 5), (3, 6)]

What does *m mean in this example and how does it do the magic here?


There's a good writeup on args/kwargs at

http://www.megasolutions.net/python/-args-and---kwargs-78766.aspx

(looks like the content was gleaned from comp.lang.python and 
credited)


-tkc



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pygccxml xml output file

[whatazor]

Hi all,
I start to use this module in order to produce xml( and the make other
things), but differently from gccxml I don't find the variable that
set the name of the xml output file after the parsing (in gccxml is -
fxml), so it creates temporary files.
how can I do an Is there a tutorial that explain with dectails how it
works?

thank you,
regards

w
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Re: Porting 3.0 to 2.6 - from __future__ import super missing?

[Benjamin Peterson]

andrew cooke andrew at acooke.org writes:

 
 Hi,
 
 I have some 3.0 code, which I would like to make work with 2.6.
 However, there does not seem to be support for the new super() (no
 args) via __future__.  Is that correct?  If so, what's the best way to
 handle this?

Just use the two argument super(): super(MyClass, instance) It's supported in
both versions.




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Re: What's the business with the asterisk?

[Kay Schluehr]

On 24 Jan., 13:31, mk mrk...@gmail.com wrote:
 Hello everyone,

  From time to time I spot an asterisk (*) used in the Python code
 _outside_ the usual *args or **kwargs application.

 E.g. here:http://www.norvig.com/python-lisp.html

 def transpose (m):
    return zip(*m)
   transpose([[1,2,3], [4,5,6]])
 [(1, 4), (2, 5), (3, 6)]

 What does *m mean in this example and how does it do the magic here?

 Regards,
 mk

If zip is specified as

def zip(*args):
...

one can pass zero or more arguments into zip. In the zip body one has
access to the argument tuple args. So zip(a, b, c) yields args = (a,
b, c). Now suppose you want to pass the tuple t = (a, b, c) to zip. If
you call zip(t) then args = ((a, b, c),). When calling zip(*t) instead
the tuple is passed as variable arguments just like they are specified
in the signature of zip. So args = (a, b, c).

Same holds for

def foo(**kwd):
...

and foo(**kwd) versus foo(kwd).
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Re: What is intvar?

[W. eWatson]

W. eWatson wrote:

r wrote:

here is a good explanation of control vars:
http://infohost.nmt.edu/tcc/help/pubs/tkinter/control-variables.html

Here are 3 great Tkinter refernces in order:
http://infohost.nmt.edu/tcc/help/pubs/tkinter/
http://effbot.org/tkinterbook/
http://www.pythonware.com/library/tkinter/introduction/

Thanks to all for the reference and tips.

tkinterbook is easy to follow, but it seems to have been abandoned in 2005. 
Did it appear in another guise somewhere else?


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 (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
  Obz Site:  39° 15' 7 N, 121° 2' 32 W, 2700 feet

Web Page: www.speckledwithstars.net/

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Re: Porting 3.0 to 2.6 - from __future__ import super missing?

[andrew cooke]

On Jan 24, 10:39 am, Benjamin Peterson benja...@python.org wrote:
 andrew cooke andrew at acooke.org writes:



  Hi,

  I have some 3.0 code, which I would like to make work with 2.6.
  However, there does not seem to be support for the new super() (no
  args) via __future__.  Is that correct?  If so, what's the best way to
  handle this?

 Just use the two argument super(): super(MyClass, instance) It's supported in
 both versions.

Thanks.  Any idea how to deal with ABCs?  It's sufficient to use a
simple class, but I want to expose an ABC in 3.0 as it will make it
easier for others to extend.

Unfortunately, metaclass= is a syntax error in 2.6 so the following
still fails:

from sys import version

if version.startswith('2.'):
class Matcher():
pass
else:
class Matcher(metaclass=ABCMeta):
pass

Andrew
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Re: OCaml, Language syntax, and Proof Systems

[Joe Riopel]

On Fri, Jan 23, 2009 at 6:16 PM, Xah Lee xah...@gmail.com wrote:
 The haskell tutorials you can find online are the most mothefucking
 stupid unreadable fuck. The Haskll community is almost stupid. What
 they talk all day is about monads, currying, linder myer fuck type.
 That's what they talk about all day. All day and night. Monad!  What's
 a monad! The importance of monad! How to learn monad! Simple intro to
 monad! Fucking morons, but MONAD!

http://www.youtube.com/watch?v=9fohXBj2UEI
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Re: Counter Class -- Bag/Multiset

[pataphor]

On Thu, 22 Jan 2009 10:11:37 -0800 (PST)
Raymond Hettinger pyt...@rcn.com wrote:

 The collections module in Python 2.7 and Python 3.1 has gotten a new
 Counter class that works like bags and multisets in other languages.

I like that! Now that we have a multiset or Counter I think a
redefinition of itertools.permutations is in order.

For example something like this:

def genperm(D, R = []):
#generate the permutations of a multiset
if not max(D.values()):
yield tuple(R)
else:
for k,v in sorted(D.items()):
if v: 
D[k] -= 1
for g in genperm(D,R+[k]): 
yield g
D[k] += 1

def perm(seq):
D = {}
for x in seq:
D[x] = D.get(x,0)+1
for X in genperm(D):
yield X

def test():
for i,x in enumerate(perm('aabbcc')):
print i,x
print len(set(perm('aabbcc')))

if __name__ == '__main__':
test()

The dictionary I'm using here could be seamlessly replaced by your
Counter class.

By the way, I like your itertools recipes a lot, but I miss something
that repeats elements n times, an xcycle or ncycle or whatever, like I
used in this (older code, sorry for the name overlap):

def repeat(x,n = 0):
i = 0
while i  n :
yield x
i += 1

def xcycle(seq,n):
while 1:
for x in seq:
for y in repeat(x,n):
yield y

def counter(symbols,width):
base = len(symbols)
R = []
k = width
while k:
k -= 1
R.append(xcycle(symbols,base**k))
nc = base**width
while nc:
yield list(x.next() for x in R)
nc -=1

def test():
symbols = '01'
width = 4
for state in counter(symbols,width):
print state

if __name__=='__main__':
test()

I think such a thing could be handy for generating more kinds of
periodic sequences. By the way, itertools is starting to feel like it's
becoming some sort of alternate programming design all by itself. I
wonder when it is going to break loose from python! I like that
way of thinking a lot, thanks.

P.

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Doc for extended call syntax; was: Re: unzip array of arrays?

[Bryan Olson]

Tobiah wrote:

Where can I read about
this mysterious use of the '*'?


Hmmm... that's a harder question than I thought. Am I missing it, or 
does Python's doc need a write-up of the extended call syntax?



It only works in the
context of the zip() function.  It's hard to understand
how the interpreter handles that.


It works generally, for any callable. See the doc for 'apply':

http://docs.python.org/library/functions.html#non-essential-built-in-functions

It not only works in a call, but also in function definitions. You can 
call a function with the extended call syntax whether or not is defined 
with * and ** arguments.



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Re: Mathematica 7 compares to other languages

[Jerry Gerrone]

On Jan 21, 1:06 pm, soul.mirr...@gmail.com soul.mirr...@gmail.com
wrote:
 On Dec 4 2008, 5:11 am, Andreas Waldenburger geekm...@usenot.de
 wrote:
  I vaguely remember you plonking [Xah Lee] before. Did you unplonk him in
  the meantime? Or was that just a figure of speech?

  teasingly yours,
  /W

 Andreas Waldenburger, I hold up a mirror to your soul!

 A couple of years ago you started posting to the newsgroup
 comp.lang.java.programmer. Unlike most newbies, instead of lurking for
 a while and then contributing on-topic posts about Java, you jumped
 into the nearest available flamewar and immediately got in up to your
 neck. Then, on November 13, 2007, you stooped to intentionally
 misquoting one of your opponents. When he wrote

 http://groups.google.com/group/comp.lang.java.programmer/msg/7797d4e9...

 A few days later, you did it again, misquoting this post

 http://groups.google.com/group/comp.lang.java.programmer/msg/fca19d41...

 in this one:

 http://groups.google.com/group/comp.lang.java.programmer/msg/397e1d4b...

 In both cases, you publicly portrayed this poor man as a pervert, even
 though, whatever his other [insult deleted], that is clearly not one of
 them.

None of the nasty things that you have said or implied about me are at
all true.

 Repeatedly you have claimed to be primarily motivated by finding the
 disrupting of newsgroups to be entertaining. This is tantamount to
 admitting to being a troll.

Yes, and here you are, feeding him. Way to go, genius.

(And cljp had just gotten peaceful again, too!)
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understanding nested lists?

[Vincent Davis]

I have a short peace of code that is not doing what I expect. when I assign
a value to a list in a list alist[2][4]=z this seems replace all the 4
elements in all the sub lists. I assume it is supposed to but this is not
what I expect. How would I assign a value to the 4th element in the 2nd
sublist. here is the code I have. All the printed values are what I would
expect except that all sublist values are replaced.
Thanks for your help
Vincent

on the first iteration I get ;
new_list [[None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None], [None,
0, 1, None], [None, 0, 1, None], [None, 0, 1, None]]

and expected this;
new_list [[None, 0, 1, None], [None, None, None, None], [None, None, None,
None], [None, None, None, None], [None, None, None, None],
[None, None, None, None]]

Code;
list1=[[1,2],[0,3,2,1],[0,1,3],[2,0,1],[3],[2,3]]
new_list=[[None]*4]*6
print 'new_list',new_list
for sublist in range(6): # 6 becuase it is the # of rows lists1
print 'sublist', sublist
for x in list1[sublist]:
print list1[sublist]
print 'new_list[sublist][x]', new_list[sublist][x]
new_list[sublist][x]=list1[sublist].index(x)
print 'sublist', sublist, 'x', x
print new_list[sublist][x]
print 'new_list', new_list
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String comparision

[S.Selvam Siva]

Hi all,

I am developing spell checker for my local language(tamil) using python.
I need to generate alternative word list for a miss-spelled word from the
dictionary of words.The alternatives must be as much as closer to the
miss-spelled word.As we know, ordinary string comparison wont work here .
Any suggestion for this problem is welcome.

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practical limits of urlopen()

[webcomm]

Hi,

Am I going to have problems if I use urlopen() in a loop to get data
from 3000+ URLs?  There will be about 2KB of data on average at each
URL.  I will probably run the script about twice per day.  Data from
each URL will be saved to my database.

I'm asking because I've never opened that many URLs before in a loop.
I'm just wondering if it will be particularly taxing for my server.
Is it very uncommon to get data from so many URLs in a script?  I
guess search spiders do it, so I should be able to as well?

Thank you,
Ryan
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Re: Porting 3.0 to 2.6 - from __future__ import super missing?

[Benjamin Peterson]

andrew cooke andrew at acooke.org writes:
 Unfortunately, metaclass= is a syntax error in 2.6 so the following
 still fails:
 
 from sys import version
 
 if version.startswith('2.'):
 class Matcher():
 pass
 else:
 class Matcher(metaclass=ABCMeta):
 pass

I would suggest that you use the 2.6 syntax, and run 2to3 -f metaclass on your
code. (ABCs have been backported to 2.6.)




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Re: Web authentication urllib2

[Steve Holden]

Gabriel wrote:
 Yep, i realize this a minute after posting, sorry.
 
 And thank you again .)
 
A pleasure. Next time, you might consider posting an explanation along
with the it's working now message, just to give closure to the thread
for anyone who ends up reading it later after a search.

Good that you got your problem solved, anyway!

regards
 Steve
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Re: understanding nested lists?

[Steve Holden]

Vincent Davis wrote:
 I have a short peace of code that is not doing what I expect. when I
 assign a value to a list in a list alist[2][4]=z this seems replace all
 the 4 elements in all the sub lists. I assume it is supposed to but this
 is not what I expect. How would I assign a value to the 4th element in
 the 2nd sublist. here is the code I have. All the printed values are
 what I would expect except that all sublist values are replaced.
 
 Thanks for your help
 Vincent
 
 on the first iteration I get ;
 new_list [[None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None],
 [None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None]]
 
 and expected this;
 new_list [[None, 0, 1, None], [None, None, None, None],
 [None, None, None, None], [None, None, None, None], [None, None, None,
 None], [None, None, None, None]]
 
 Code;
 list1=[[1,2],[0,3,2,1],[0,1,3],[2,0,1],[3],[2,3]]
 new_list=[[None]*4]*6
 print 'new_list',new_list
 for sublist in range(6): # 6 becuase it is the # of rows lists1
 print 'sublist', sublist
 for x in list1[sublist]:
 print list1[sublist]
 print 'new_list[sublist][x]', new_list[sublist][x]
 new_list[sublist][x]=list1[sublist].index(x)
 print 'sublist', sublist, 'x', x
 print new_list[sublist][x]
 print 'new_list', new_list
 
When you create new_list you are actually filling it with six references
to the same list. Consequently when you change one of those list
elements they all appear to change (because they are all referencing the
same list object).

Try instead

new_list = [[None]*4 for i in range(6)]

and you should find your code works as expected. In this case the list
is constructed with a new sublist as each element.

regards
 Steve
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Re: understanding nested lists?

[Brian Allen Vanderburg II]

vinc...@vincentdavis.net wrote:
I have a short peace of code that is not doing what I expect. when I 
assign a value to a list in a list alist[2][4]=z this seems replace 
all the 4 elements in all the sub lists. I assume it is supposed to 
but this is not what I expect. How would I assign a value to the 4th 
element in the 2nd sublist. here is the code I have. All the printed 
values are what I would expect except that all sublist values are 
replaced.


Thanks for your help
Vincent

on the first iteration I get ;
new_list [[None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None], 
[None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None]]


and expected this;
new_list [[None, 0, 1, None], [None, None, None, None], 
[None, None, None, None], [None, None, None, None], [None, None, None, 
None], [None, None, None, None]]


Code;
list1=[[1,2],[0,3,2,1],[0,1,3],[2,0,1],[3],[2,3]]
new_list=[[None]*4]*6
print 'new_list',new_list
for sublist in range(6): # 6 becuase it is the # of rows lists1
print 'sublist', sublist
for x in list1[sublist]:
print list1[sublist]
print 'new_list[sublist][x]', new_list[sublist][x]
new_list[sublist][x]=list1[sublist].index(x)
print 'sublist', sublist, 'x', x
print new_list[sublist][x]
print 'new_list', new_list



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The problem is likely this right here:

[[None]*4]*6

This first creates an inner list that has 4 Nones, then the outer list 
contains 6 references to that same list, so (new_list[0] is new_list[1]) 
and (new_list[1] is new_list[2]).  I make this mistake a lot myself.


l=[[None]*4]*6
print id(l[0])  # -1210893364
print id(l[1])  # -1210893364

l = [list([None]*4) for x in range(6)]
print id(l[0])  # -1210893612
print id(l[1])  # -1210893580

Works better

Brian Vanderburg II
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Re: Two import questions in Python 3.0

[Scott David Daniels]

Kay Schluehr wrote:

On 24 Jan., 09:21, Gabriel Genellina gagsl-...@yahoo.com.ar wrote:

If you run A.py as a script, it does not know it lives inside a package.
You must *import* A for it to become aware of the package.
Also, the directory containing the script comes earlier than PYTHONPATH
entries in sys.path -- so watch for that case too.

Thanks, yes. I always make the same error thinking that a directory
with the ritual __init__ file is actually a package ( as some kind of
platonic entity ), something that is more obvious to me than it is to
the runtime. The relative import semantics introduced with Python 2.5
has made the error just visible that was hidden to me for about a
decade. Shit.

Temper the language a bit.  You lose your effectiveness by some people
reading the color of your words, rather than their meaning in code.

By the way, if you run the script as:

$ python -m package.A

You may get what you want

demo (language fixed up a bit, moe info printed):

in .../lib/site-packages:
possible.py
-
print('import from top possible: %s' % __file__)

in .../lib/site-packages/package:
possible.py
-
print('import from package.possible: %s' % __file__)

__init__.py
-
print('package initialized: %s' % __file__)


A.py
--
print('A started: %s' % __file__)
import possible
print('A running: %s' % __file__)

--Scott David Daniels
scott.dani...@acm.org
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Re: practical limits of urlopen()

[Steve Holden]

webcomm wrote:
 Hi,
 
 Am I going to have problems if I use urlopen() in a loop to get data
 from 3000+ URLs?  There will be about 2KB of data on average at each
 URL.  I will probably run the script about twice per day.  Data from
 each URL will be saved to my database.
 
 I'm asking because I've never opened that many URLs before in a loop.
 I'm just wondering if it will be particularly taxing for my server.
 Is it very uncommon to get data from so many URLs in a script?  I
 guess search spiders do it, so I should be able to as well?
 
You shouldn't expect problem - though you might want to think about
using some more advanced technique like threading to get your results
more quickly.

This is Python, though. It shouldn't take long to write a test program
to verify that you can indeed spider 3,000 pages this way.

With about 2KB per page, you could probably build up a memory structure
containing the whole content of every page without memory usage becoming
too excessive for modern systems. If you are writing stuff out to a
database as you go and not retaining page content then there should be
no problems whatsoever.

Then look at a parallelized solution of some sort if you need it to work
more quickly.

regards
 Steve
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RegEx issues

[Sean Brown]

Using python 2.4.4 on OpenSolaris 2008.11

I have the following string created by opening a url that has the
following string in it:

td[ct] = [[ ... ]];\r\n

The ...  above is what I'm interested in extracting which is really a
whole bunch of text. So I think the regex \[\[(.*)\]\]; should do it.
The problem is it appears that python is escaping the \ in the regex
because I see this:

reg = '\[\[(.*)\]\];'
reg

'\\[\\[(.*)\\]\\];'

Now to me looks like it would match the string - \[\[ ... \]\];

Which obviously doesn't match anything because there are no literal \ in
the above string. Leaving the \ out of the \[\[ above has re.compile
throw an error because [ is a special regex character. Which is why it
needs to be escaped in the first place.

I am either doing something really wrong, which very possible, or I've
missed something obvious. Either way, I thought I'd ask why this isn't
working and why it seems to be changing my regex to something else.
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Parsing a string into a datetime object

[Mark.Petrovic]

Good day.

Might someone comment on why %f is not accepted as a valid field
directive in:

 from datetime import datetime
 created=2009-01-24 16:04:55.882788
 dt = datetime.strptime(created,%Y-%m-%d %H:%M:%S.%f)
Traceback (most recent call last):
  File stdin, line 1, in module
  File /System/Library/Frameworks/Python.framework/Versions/2.5/lib/
python2.5/_strptime.py, line 321, in strptime
(bad_directive, format))
ValueError: 'f' is a bad directive in format '%Y-%m-%d %H:%M:%S.%f'

This is for Python 2.5.1 under OS X.

Thank you.
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Re: RegEx issues

[Mark Tolonen]

Sean Brown sbrown.h...@[spammy] gmail.com wrote in message 
news:glflaj$qr...@nntp.motzarella.org...

Using python 2.4.4 on OpenSolaris 2008.11

I have the following string created by opening a url that has the
following string in it:

td[ct] = [[ ... ]];\r\n

The ...  above is what I'm interested in extracting which is really a
whole bunch of text. So I think the regex \[\[(.*)\]\]; should do it.
The problem is it appears that python is escaping the \ in the regex
because I see this:

reg = '\[\[(.*)\]\];'
reg

'\\[\\[(.*)\\]\\];'

Now to me looks like it would match the string - \[\[ ... \]\];


You are viewing the repr of the string


reg='\[\[(.*)\]\];'
reg

'\\[\\[(.*)\\]\\];'

print reg

\[\[(.*)\]\];== these are the chars passed to regex

The slashes are telling regex the the [ are literal.



Which obviously doesn't match anything because there are no literal \ in
the above string. Leaving the \ out of the \[\[ above has re.compile
throw an error because [ is a special regex character. Which is why it
needs to be escaped in the first place.

I am either doing something really wrong, which very possible, or I've
missed something obvious. Either way, I thought I'd ask why this isn't
working and why it seems to be changing my regex to something else.


Did you try it?


s='td[ct] = [[blah blah]];\r\n'
re.search(reg,s).group(1)

'blah blah'

-Mark


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Re: What is intvar?

[Steve Holden]

W. eWatson wrote:
 W. eWatson wrote:
 r wrote:
 here is a good explanation of control vars:
 http://infohost.nmt.edu/tcc/help/pubs/tkinter/control-variables.html

 Here are 3 great Tkinter refernces in order:
 http://infohost.nmt.edu/tcc/help/pubs/tkinter/
 http://effbot.org/tkinterbook/
 http://www.pythonware.com/library/tkinter/introduction/
 Thanks to all for the reference and tips.

 tkinterbook is easy to follow, but it seems to have been abandoned in
 2005. Did it appear in another guise somewhere else?
 
There hasn't been a lot of development on Tkinter in the intervening
period. It's a mature system, so there has been no need to update the
documentation.

regards
 Steve
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Re: Web authentication urllib2

[Scott David Daniels]

Gabriel wrote:

Yep, i realize this a minute after posting, sorry.

And thank you again .)

Steve Holden wrote:

...

I'll offer a couple of pointers about what we all expect here.
Please treat this as advice, not a shout of disapproval.

(1) Do not top post (put your response above the previous interaction).
(2) When quoting previous interactions, cut until the portion you are
quoting provides enough context to make your post's context
comprehensible, but only that much context.
(3) When you figure out you problem, especially on your own, summarize
back in a final message what went wrong and how you fixed it.

The reasons for these three rules are:
(1) The message can be read in order, rather than reading up and down.
(2) People _do_ have access to the previous messages (albeit sometimes
only with some effort).  The message should be comprehensible on its
own, but your reader can go back for more detail if it turns out to
be vital.  You don't want to grow your message to the point where
someone who might help you says, I don't have time to read that.
(3) Generally it is a good idea to search for answers before asking.
It can be incredibly frustrating to discover someone else had
previously seen exactly the same problem you are bashing your
head into the wall about, follow the chain, and finally read,
Never mind, I figured it out. without a clue to what was
determined.

If you read comp.lang.python for a while, you'll see this is the
norm for messages here, and these behaviors help make this a more
pleasant place to read and write.

--Scott David Daniels
scott.dani...@acm.org
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Re: Doc for extended call syntax; was: Re: unzip array of arrays?

[Steve Holden]

Bryan Olson wrote:
 Tobiah wrote:
 Where can I read about
 this mysterious use of the '*'?
 
 Hmmm... that's a harder question than I thought. Am I missing it, or
 does Python's doc need a write-up of the extended call syntax?
 
No, you aren't mistaken. Looking at the * symbol in the 2.6
documentation index it lists only two references. The first is the
language manual's explanation of its use in the def statement, the
second is a transitory reference to its use in function calls, but
that's in the tutorial where it is not likely to get much attention.

 It only works in the
 context of the zip() function.  It's hard to understand
 how the interpreter handles that.
 
 It works generally, for any callable. See the doc for 'apply':
 
 http://docs.python.org/library/functions.html#non-essential-built-in-functions
 
 
 It not only works in a call, but also in function definitions. You can
 call a function with the extended call syntax whether or not is defined
 with * and ** arguments.
 
 
regards
 Steve
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Re: Parsing a string into a datetime object

[MRAB]

Mark.Petrovic wrote:
 Good day.

 Might someone comment on why %f is not accepted as a valid field
 directive in:

 from datetime import datetime
 created=2009-01-24 16:04:55.882788
 dt = datetime.strptime(created,%Y-%m-%d %H:%M:%S.%f)
 Traceback (most recent call last):
   File stdin, line 1, in module
   File /System/Library/Frameworks/Python.framework/Versions/2.5/lib/
 python2.5/_strptime.py, line 321, in strptime
 (bad_directive, format))
 ValueError: 'f' is a bad directive in format '%Y-%m-%d %H:%M:%S.%f'

 This is for Python 2.5.1 under OS X.

 Thank you.

I believe that Python simply uses the 'strptime' (or equivalent)
function in the underlying C library: if that doesn't accept %f then
neither does Python.
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Re: RegEx issues

[Steve Holden]

Mark Tolonen wrote:
 
 Sean Brown sbrown.h...@[spammy] gmail.com wrote in message
 news:glflaj$qr...@nntp.motzarella.org...
 Using python 2.4.4 on OpenSolaris 2008.11

 I have the following string created by opening a url that has the
 following string in it:

 td[ct] = [[ ... ]];\r\n

 The ...  above is what I'm interested in extracting which is really a
 whole bunch of text. So I think the regex \[\[(.*)\]\]; should do it.
 The problem is it appears that python is escaping the \ in the regex
 because I see this:
 reg = '\[\[(.*)\]\];'
 reg
 '\\[\\[(.*)\\]\\];'

 Now to me looks like it would match the string - \[\[ ... \]\];
 
 You are viewing the repr of the string
 
 reg='\[\[(.*)\]\];'
 reg
 '\\[\\[(.*)\\]\\];'
 print reg
 \[\[(.*)\]\];== these are the chars passed to regex
 
 The slashes are telling regex the the [ are literal.
 

 Which obviously doesn't match anything because there are no literal \ in
 the above string. Leaving the \ out of the \[\[ above has re.compile
 throw an error because [ is a special regex character. Which is why it
 needs to be escaped in the first place.

 I am either doing something really wrong, which very possible, or I've
 missed something obvious. Either way, I thought I'd ask why this isn't
 working and why it seems to be changing my regex to something else.
 
 Did you try it?
 
 s='td[ct] = [[blah blah]];\r\n'
 re.search(reg,s).group(1)
 'blah blah'
 
Beware, though, that by default regex matches are greedy, so if there's
a chance that two [[ ... ]] [[ ... ]] can appear on the same line then
the above pattern will match

  ... ]] [[ ...

regards
 Steve
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Byte oriented data types in python

[Ravi]

I have following packet format which I have to send over Bluetooth.

packet_type (1 byte unsigned) || packet_length (1 byte unsigned) ||
packet_data(variable)

How to construct these using python data types, as int and float have
no limits and their sizes are not well defined.
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Re: RegEx issues

[Roy Smith]

Sean Brown sbrown.h...@[spammy]gmail.com wrote:

 The problem is it appears that python is escaping the \ in the regex
 because I see this:
 reg = '\[\[(.*)\]\];'

The first trick of working with regexes in Python is to *always* use raw 
strings.  Instead of

reg = '\[\[(.*)\]\];'

you want

reg = r'\[\[(.*)\]\];'

In this case, I think it ends up not mattering, but it's one less thing to 
worry about.  Next, when looking at something like

  reg
 '\\[\\[(.*)\\]\\];'

it's hard to see exactly what all the backslashes mean.  Which are real and 
which are escapes?  Try doing

 print reg
\[\[(.*)\]\];

which gets you the str(reg) instead of repr(reg).  Another trick when 
you're not 100% what you're looking at is to explode the string like this:

 [c for c in reg]
['\\', '[', '\\', '[', '(', '.', '*', ')', '\\', ']', '\\', ']', ';']
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Re: RegEx issues

[Scott David Daniels]

Sean Brown wrote:

I have the following string ...:  td[ct] = [[ ... ]];\r\n
The ... (representing text in the string) is what I'm extracting 
So I think the regex \[\[(.*)\]\]; should do it.
The problem is it appears that python is escaping the \ in the regex
because I see this:

reg = '\[\[(.*)\]\];'
reg

'\\[\\[(.*)\\]\\];'
Now to me looks like it would match the string - \[\[ ... \]\];
...


OK, you already have a good answer as to what is happening.
I'll mention that raw strings were put in the language exactly for
regex work.  They are useful for any time you need to use the backslash
character (\) within a string (but not as the final character).
For example:
len(r'\a\b\c\d\e\f\g\h') == 16 and len('\a\b\c\d\e\f\g\h') == 13

If you get in the habit of typing regex strings as r'...' or r...,
and examining the patters with print(somestring), you'll ease your life.

--Scott David Daniels
scott.dani...@acm.org
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Re: Porting 3.0 to 2.6 - from __future__ import super missing?

[andrew cooke]

On Jan 24, 2:32 pm, Benjamin Peterson benja...@python.org wrote:
 I would suggest that you use the 2.6 syntax, and run 2to3 -f metaclass on 
 your
 code. (ABCs have been backported to 2.6.)

Thanks - with that hint I found this -
http://mikewatkins.ca/2008/11/29/python-2-and-3-metaclasses/#using-the-metaclass-in-python-2-x-and-3-x

Andrew
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TEST=`which test` equivalent in python?

[Jay Jesus Amorin]

Hi,

Kindly help.

import sys, os, string

*SVNLOOK_PATH=os.system('which svnlook')*

def main(repos, txn):
svnlook_cmd = '%s log -t %s %s' % (*SVNLOOK_PATH*, txn, repos)
check_msg = os.popen(svnlook_cmd, 'r').readline().rstrip('\n')

if len(check_msg)  10:
sys.stderr.write (Blahh Blahh\n)
sys.exit(1)
else:
sys.exit(0)

if __name__ == '__main__':
if len(sys.argv)  3:
sys.stderr.write(Usage: %s REPOS TXN\n % (sys.argv[0]))
else:
main(sys.argv[1], sys.argv[2])


The SVNLOOK_PATH is not working and python says its null when run as SVN
hook-script. Do I need to load the os environment variable? How do i pass
the value of 'which svnlook' to SVNLOOK_PATH variable.

Thanks for your help.


Jay
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Re: Parsing a string into a datetime object

[Hrvoje Niksic]

Mark.Petrovic mspetro...@gmail.com writes:

 Might someone comment on why %f is not accepted as a valid field
 directive in:

 from datetime import datetime
 created=2009-01-24 16:04:55.882788
 dt = datetime.strptime(created,%Y-%m-%d %H:%M:%S.%f)
 Traceback (most recent call last):
   File stdin, line 1, in module
   File /System/Library/Frameworks/Python.framework/Versions/2.5/lib/
 python2.5/_strptime.py, line 321, in strptime
 (bad_directive, format))
 ValueError: 'f' is a bad directive in format '%Y-%m-%d %H:%M:%S.%f'

 This is for Python 2.5.1 under OS X.

time.strptime is documented to use the same set of directives as
time.strftime, and
http://docs.python.org/library/time.html#time.strftime doesn't mention
a %f directive.
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Re: Byte oriented data types in python

[Stephen Hansen]

I have following packet format which I have to send over Bluetooth.

 packet_type (1 byte unsigned) || packet_length (1 byte unsigned) ||
 packet_data(variable)

 How to construct these using python data types, as int and float have
 no limits and their sizes are not well defined.


Check out the struct module.

You want something like:

  data = struct.pack(BB4s, 1, 4, this)

It returns a string of bytes according to the specification -- B is unsigned
byte, and 4s is a string of 4 characters. The 1 feeds into the first byte,
the 4 into the second, etc.

--Stephen
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Re: TEST=`which test` equivalent in python?

[Benjamin Kaplan]

On Sat, Jan 24, 2009 at 2:03 PM, Jay Jesus Amorin jay.amo...@gmail.comwrote:

 Hi,

 Kindly help.

 import sys, os, string

 *SVNLOOK_PATH=os.system('which svnlook')*


Read the docs on os.system. It returns the program's return code, not the
child processes stdout. Use the subprocess module.



 def main(repos, txn):
 svnlook_cmd = '%s log -t %s %s' % (*SVNLOOK_PATH*, txn, repos)
 check_msg = os.popen(svnlook_cmd, 'r').readline().rstrip('\n')


os.popen does what you want here, but it is deprecated in favor of the more
powerful subprocess module.



 if len(check_msg)  10:
 sys.stderr.write (Blahh Blahh\n)
 sys.exit(1)
 else:
 sys.exit(0)

 if __name__ == '__main__':
 if len(sys.argv)  3:
 sys.stderr.write(Usage: %s REPOS TXN\n % (sys.argv[0]))
 else:
 main(sys.argv[1], sys.argv[2])


 The SVNLOOK_PATH is not working and python says its null when run as SVN
 hook-script. Do I need to load the os environment variable? How do i pass
 the value of 'which svnlook' to SVNLOOK_PATH variable.

 Thanks for your help.


 Jay

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Re: RegEx issues

[MRAB]

Roy Smith wrote:
[snip]

Another trick when you're not 100% what you're looking at is to
explode the string like this:


 [c for c in reg]
 ['\\', '[', '\\', '[', '(', '.', '*', ')', '\\', ']', '\\', ']', ';']

A shorter way is list(reg).
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Re: ossaudiodev problem: sawtooth noise

[Peter Pearson]

On Fri, 23 Jan 2009 14:55:36 -0200, Gabriel Genellina wrote:
 En Fri, 23 Jan 2009 14:36:46 -0200, Peter Pearson  
ppear...@nowhere.invalid escribió:
 On Thu, 22 Jan 2009 20:58:14 -0200, Gabriel Genellina wrote:
 En Mon, 19 Jan 2009 21:57:04 -0200, Peter Pearson
 ppear...@nowhere.invalid escribió:

 The following code uses ossaudiodev to read 1000 values from
 my sound card at a rate of 12,000 samples per second:

 When I select a sample rate that is not a power of 2 times
 3000 samples/second, a strong and very regular sawtooth is
 superimposed on the signal.  At some sampling frequencies,
 it appears as a rising sawtooth, and at other sampling
 frequencies it is a declining sawtooth, so I'm presumably
 lost in some aliasing wilderness.  As best I can tell,
 it's a 48 KHz sawtooth.

 That could be a hardware and/or driver limitation. By example, an
 AC97-compliant chipset may provide a fixed rate of 48000 samples/second  
 any sample rate conversion must be done by other means, if possible at  
 all.

 Oh!  As a matter of fact, my soundcard *is* AC97-compliant
 (VT8233/A/8235/8237, according to Sysinfo).  So . . . this
 sawtooth might result from some software, somewhere in the bucket
 brigade between me and the hardware, attempting to perform
 sample-rate conversion?  The 48 KHz coincidence seems very
 significant.

 Yep. Google found this for me:
 http://mail-index.netbsd.org/port-i386/2003/02/18/0003.html

 Using a sample rate that is a sub-multiple of 48000 is perhaps a safe  
 approach.

Back around the time I installed Ubuntu's Hardy Heron, several
copies of this line appeared in /var/log/user.log.0:
Jan  4 21:32:53 eleodes pulseaudio[6437]: alsa-util.c: \
   Device front:0 doesn't support 44100 Hz, changed to 48000 Hz.

So I suppose I'll just restrict myself to well-behaved frequencies.
I'm not sure what sub-multiple means, but all the successful
frequencies I've found over 1 KHz have been multiples of 1.5 KHz that
evenly divide 48 KHz.  Frequencies showing large sawtooths include
2, 4, 8, 10, and 16 KHz.

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Re: Byte oriented data types in python

[Martin v. Löwis]

 packet_type (1 byte unsigned) || packet_length (1 byte unsigned) ||
 packet_data(variable)
 
 How to construct these using python data types, as int and float have
 no limits and their sizes are not well defined.

In Python 2.x, use the regular string type: chr(n) will create a single
byte, and the + operator will do the concatenation.

In Python 3.x, use the bytes type (bytes() instead of chr()).

Regards,
Martin
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Re: Byte oriented data types in python

[skip]

Ravi packet_type (1 byte unsigned) || packet_length (1 byte unsigned) ||
Ravi packet_data(variable)

Ravi How to construct these using python data types, as int and float have
Ravi no limits and their sizes are not well defined.

Take a look at the struct and ctypes modules.

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MaxInt on Vista-64bit?

[googler . 1 . webmaster]

Hi!

I downloaded Python64 for Windows Vista64 but the value returned from
sys.maxint is just a 32bit integer. I found out, thats by design,
Microsoft decided to make the long value 32bit. What can I do to
compile python 2.6 with maxint of 64bit integers?

Can I replace the int values to a int64 value?


Thanks a lot!
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Re: understanding nested lists?

[Vincent Davis]

Thanks for the info. I did not know that.
Thanks
Vincent Davis



On Sat, Jan 24, 2009 at 10:46 AM, Steve Holden st...@holdenweb.com wrote:

 Vincent Davis wrote:
  I have a short peace of code that is not doing what I expect. when I
  assign a value to a list in a list alist[2][4]=z this seems replace all
  the 4 elements in all the sub lists. I assume it is supposed to but this
  is not what I expect. How would I assign a value to the 4th element in
  the 2nd sublist. here is the code I have. All the printed values are
  what I would expect except that all sublist values are replaced.
 
  Thanks for your help
  Vincent
 
  on the first iteration I get ;
  new_list [[None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None],
  [None, 0, 1, None], [None, 0, 1, None], [None, 0, 1, None]]
 
  and expected this;
  new_list [[None, 0, 1, None], [None, None, None, None],
  [None, None, None, None], [None, None, None, None], [None, None, None,
  None], [None, None, None, None]]
 
  Code;
  list1=[[1,2],[0,3,2,1],[0,1,3],[2,0,1],[3],[2,3]]
  new_list=[[None]*4]*6
  print 'new_list',new_list
  for sublist in range(6): # 6 becuase it is the # of rows lists1
  print 'sublist', sublist
  for x in list1[sublist]:
  print list1[sublist]
  print 'new_list[sublist][x]', new_list[sublist][x]
  new_list[sublist][x]=list1[sublist].index(x)
  print 'sublist', sublist, 'x', x
  print new_list[sublist][x]
  print 'new_list', new_list
 
 When you create new_list you are actually filling it with six references
 to the same list. Consequently when you change one of those list
 elements they all appear to change (because they are all referencing the
 same list object).

 Try instead

 new_list = [[None]*4 for i in range(6)]

 and you should find your code works as expected. In this case the list
 is constructed with a new sublist as each element.

 regards
  Steve
 --
 Steve Holden+1 571 484 6266   +1 800 494 3119
 Holden Web LLC  http://www.holdenweb.com/

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Re: Why GIL? (was Re: what's the point of rpython?)

[Carl Banks]

On Jan 24, 12:40 am, Gabriel Genellina gagsl-...@yahoo.com.ar
wrote:
 En Sat, 24 Jan 2009 06:06:02 -0200, Carl Banks pavlovevide...@gmail.com  
 escribió:



  On Jan 23, 11:45 pm, Bryan Olson fakeaddr...@nowhere.org wrote:
  Carl Banks wrote:
   Classes in Python are mutable types, usually.  Class instances are
   (except for the refcount) immutable objects, usually.

  There's where we disagree. I assert that class instances are usually
  mutable objects.

  Nope, you're dead wrong, nothing more to it.  The bits of a class
  instance never change.  The __dict__ is a mutable object.  The class
  instance itself isn't.  It's not reasonable to call an object whose
  bits can't change a mutable obect.

  Anyway, all you're doing is distracting attention from my claim that
  instance objects wouldn't need to be locked.  They wouldn't, no matter
  how mutable you insist these objects whose bits would never change
  are.

 Me too, I don't get what you mean. Consider a list instance, it contains a  
 count of allocated elements, and a pointer to some memory block. They  
 change when the list is resized. This counts as mutable to me. I really  
 don't understand your claim.


Yeah, yeah, I know that, and in the bickering that ensued some aspects
of the original context were lost.  I should really not have been
pulled into Bryan's strawman over the definition of immutable, since
it's just a label, I oughtn't give a damn what it's called, I only
care what it does.  I didn't handle this repartee very well.

Anyway, it goes back to the original vision for a mark-and-sweep
Python language as I presented what seems like a long time ago.

I presented the type system that had three base metatypes instead of
the one base metatype we have now: immutable_type, mutable_type, and
mutable_dict_type.  The default metatype for Python classes would be
mutable_dict_type, which is a type wherein the object itself would be
mutable but it would still have all the mutator methods __init__,
__setattr__, etc., but they could only act on the __dict__.
mutable_dict_types would not be allowed to define any slots, and
__dict__ wouldn't be reassignable.  (However, it seems reasonable to
allow the base tp_new to accept a dict argument.)

OTOTH, list's metatype would be mutable_type, so the type object
itself would be mutable.

Bryan claimed that that would be a very different language from
Python, apparently because it hadn't occurred to him that by-and-
large, the instance itself doesn't change, only the dict does.
Perhaps Bryan was thinking of __dict__'s reassignability (that
certainly didn't occur to me); if he was I apologize for my snideness.

HAVING SAID THAT, I still still say what I proposed would not be a
radically different language from Python.  A little different, of
course.  Much slower, almost certainly.


Carl Banks
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Re: MaxInt on Vista-64bit?

[Martin v. Löwis]

 I downloaded Python64 for Windows Vista64 but the value returned from
 sys.maxint is just a 32bit integer. I found out, thats by design,
 Microsoft decided to make the long value 32bit. What can I do to
 compile python 2.6 with maxint of 64bit integers?

At a minimum, you need to change ob_ival to a 64-bit type in
PyIntObject. Consequentially, you probably need to change a lot
of other functions, e.g. PyInt_AsLong should probably also return
a 64-bit integer (as should PyInt_FromLong accept one). In turn,
you will need to change all callers of these functions to adjust
their parameter types. And so on.

 Can I replace the int values to a int64 value?

See above. In short: no. Use a real 64-bit operating system
(such as 64-bit Linux, Solaris, FreeBSD, etc)

Regards,
Martin

P.S. I do wonder why you want to do this, though. Isn't Python's
long integer type good enough?
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Re: MaxInt on Vista-64bit?

[googler . 1 . webmaster]

Hi!

Thanks for the fast answer. Yes, its enough but I never thought that
Vista64 is not a real 64-bit operating system :-o.
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Regex for Python 2.7

[MRAB]

Some time ago I discovered this difference between regular expressions
in Python and Perl:

Python

\A matches at start of string
\Z matches at end of string

Perl

\A matches at start of string
\Z matches before terminal newline or at end of string
\z matches at end of string

In Perl \A == ^ and \Z == $ in single-string mode, but in Python \A == ^
and \Z != $ in single-string mode.

Obviously, changing Python's \Z to match Perl's could break existing
code. \z could be added, but with the opposite meaning to Perl's:

Python's \Z == Perl's \z
Python's \z == Perl's \Z

Would that be confusing?

Any suggests welcome.
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Re: Why GIL?

[Carl Banks]

On Jan 24, 12:33 am, Hrvoje Niksic hnik...@xemacs.org wrote:
 Carl Banks pavlovevide...@gmail.com writes:
  Anyway, all you're doing is distracting attention from my claim that
  instance objects wouldn't need to be locked.  They wouldn't, no
  matter how mutable you insist these objects whose bits would never
  change are.

 Only if you're not implementing Python, but another language that
 doesn't support __slots__ and assignment to instance.__dict__.

I am only going to say all Python types prior to 3.0 support classes
without __slots__, so while I agree that this would be a different
language, it wouldn't necessarily be not Python.

(Python, of course, is what GvR says Python is, and he isn't going to
say that the language I presented is Python.  No worries there! :)
I'm only saying that it is conceivably similar enough to be a
different version of Python.  It would be a different language in the
same way that Python 2.6 is a different language from Python 3.0.)

Incidentally, the proposal does allow slots to be defined, but only
for actual mutable types, not for ordinary class instances.


Carl Banks
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Re: Why GIL?

[Carl Banks]

On Jan 24, 12:24 pm, Carl Banks pavlovevide...@gmail.com wrote:
 On Jan 24, 12:33 am, Hrvoje Niksic hnik...@xemacs.org wrote:

  Carl Banks pavlovevide...@gmail.com writes:
   Anyway, all you're doing is distracting attention from my claim that
   instance objects wouldn't need to be locked.  They wouldn't, no
   matter how mutable you insist these objects whose bits would never
   change are.

  Only if you're not implementing Python, but another language that
  doesn't support __slots__ and assignment to instance.__dict__.

 I am only going to say all Python types prior to 3.0 support classes
 without __slots__,

I made a mistake, and I don't want to risk confusion at this point.

all Python ***versions** prior to 3.0

and I am talking about old-style classes, of course.  Prior to 2.2 no
classes at all supported slots.


Carl Banks
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Re: Why GIL? (was Re: what's the point of rpython?)

[Carl Banks]

On Jan 24, 12:05 pm, Carl Banks pavlovevide...@gmail.com wrote:
 The default metatype for Python classes would be
 mutable_dict_type, which is a type wherein the object itself would be
 mutable but it would still have all the mutator methods __init__,
 __setattr__, etc., but they could only act on the __dict__.


Not wanting to risk confusion.

The default metatype for Python classes would be mutable_dict_type,
which is a type wherein the object itself would be ***immutable*** but
it would still have all the mutator methods __init__, __setattr__,
etc., but they could only act on the __dict__.


Carl Banks
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Re: Dynamic methods and lambda functions

[Michael Torrie]

unine...@gmail.com wrote:
 The attributes are right, but the getter are not working. The problem
 is that the lambda function always execute the last parameter passed
 for all instances of the methods. How could it be done the right way?

Basically, don't use a lambda.  Create a real, local closure with a
nested def block.  That way the closure is created every time the parent
function is called.  Lambda expressions are only ever compiled once
during execution.

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Re: Is there anyway Vpython and pyODE can be made to work with newer versions of Python 2.6.1 etc. without a lot of changes to source code?

[Gerhard Häring]

Casey Hawthorne wrote:

Is there anyway Vpython and pyODE can be made to work with newer
versions of Python 2.6.1 etc. without a lot of changes to source code?

I suppose I'm thinking of an extra layer of indirection, which might
slow things down to much.


Aren't this just Python libraries that include extension modules (i. e. 
modules written in C to interface external C libraries). If so, there is 
a good chance that just compiling them against Python 2.6 works out of 
the box. Otherwise the adjustments necessary will be just minor ones.


Python 3.0 compatibility is a different issue, though (more work).

-- Gerhard
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Re: I'm a python addict !

[Lie Ryan]

On Fri, 23 Jan 2009 19:58:09 -0700, Linuxguy123 wrote:

 I just started using python last week and I'm addicted.

you need to try this:

import antigravity

http://xkcd.com/353/

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Possible to slice a string with unpacked tuple?

[python]

Is there a way to slice a string with a tuple without unpacking
the tuple?
 myString = 111-222-333-444
 myString[ 4: 7 ]
'222'
Is there some way I could perform an identical slicing operation
with a tuple like ( 4, 7 ) without having to unpack the tuple?
 myTuple = ( 4, 7 )
Thanks!
Malcolm
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Re: Possible to slice a string with unpacked tuple?

[Benjamin Kaplan]

On Sat, Jan 24, 2009 at 5:31 PM, pyt...@bdurham.com wrote:

  Is there a way to slice a string with a tuple without unpacking the tuple?

  myString = 111-222-333-444
  myString[ 4: 7 ]
 '222'

 Is there some way I could perform an identical slicing operation with a
 tuple like ( 4, 7 ) without having to unpack the tuple?

  myTuple = ( 4, 7 )

 Thanks!
 Malcolm


1) What's wrong with unpacking the tuple?

2) Use the built-in slice.

 myString = 111-222-333-444
 myTuple = (4,7)
 mySlice = slice(*myTuple)
 myString[mySlice]
'222'
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Re: I'm a python addict !

[Benjamin Kaplan]

On Sat, Jan 24, 2009 at 5:35 PM, Lie Ryan lie.1...@gmail.com wrote:

 On Fri, 23 Jan 2009 19:58:09 -0700, Linuxguy123 wrote:

  I just started using python last week and I'm addicted.

 you need to try this:

 import antigravity

 http://xkcd.com/353/


Just be careful with that. That guy was still floating 129 comics later (3
comics = 1 week). And still going Woo Python. You can see him floating
near the peak of Mt. Everest.

http://xkcd.com/482/



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Re: Possible to slice a string with unpacked tuple?

[MRAB]

pyt...@bdurham.com wrote:

  Is there a way to slice a string with a tuple without unpacking the tuple?

  myString = 111-222-333-444
  myString[ 4: 7 ]
'222'

Is there some way I could perform an identical slicing operation with a 
tuple like ( 4, 7 ) without having to unpack the tuple?


  myTuple = ( 4, 7 )

Thanks!

Does myString[myTuple[0] : myTuple[1]] count as unpacking? If it does, 
then how about myString.__getslice__(*myTuple)?

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Re: Possible to slice a string with unpacked tuple?

[python]

Benjamin,
 Use the built-in slice.
Perfect!! That's exactly what I was looking for - I didn't know
this object existed.
 What's wrong with unpacking the tuple?
I'm extracting fields from a huge, multi-gig log file. I was
trying to avoid doing something like myString[ myTuple[ 0 ]:
myTuple[ 1 ] )  millions of times in a loop.

Thank you!
Malcolm
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Re: Possible to slice a string with unpacked tuple?

[python]

MRAB,

 Does myString[myTuple[0] : myTuple[1]] count as unpacking? 

I'm not sure my use of the term 'unpacking' was totally correct, but,
yes, that's what I was hoping to avoid with a simpler solution.

 then how about myString.__getslice__(*myTuple)?

Very interesting.

I'm going to try Ben's slice() object suggestion.

Thanks for your help,
Malcolm

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Is (-1 ==True) True or False? Neither

[oktaysafak]

Hi all,

I ran into a strange case. 

Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)] on win32
...
>>> -1 == True
False
>>> -1 == False
False

This works though:
>>> if -1:
   print "OK"

OK

After some head scratching, I realized that:
- bool is a subclass of int and that True and False evaluates to 1 and 0, so -1 is equal to neither; and 
- The if -1: statement probably works by treating -1 as bool(-1).

But I can't help finding the former comparison behavior odd. I admit that it is odd to write such code but when someone writes -1 == True, the intention is clearly a boolean comparison, not a numerical value comparison, isn't it? 

As far as I understand, to do this comparison, python is casting (loosely speaking) True to its numerical value, rather than casting -1 to its boolean value.

So, my question is: wouldn't it make more sense to do just the opposite, i.e. cast -1 to its boolean value and do a boolean comparison of the operands, when one of the operands is True or False?

Or is this too fancy? What do you think?




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Re: TEST=`which test` equivalent in python?

[Gabriel Genellina]

En Sat, 24 Jan 2009 17:03:33 -0200, Jay Jesus Amorin  
jay.amo...@gmail.com escribió:



*SVNLOOK_PATH=os.system('which svnlook')*


You've been told what's wrong with that. But instead of fixing how to  
invoke which, use distutils.spawn.find_executable instead:


py from distutils.spawn import find_executable
py find_executable('svnlook')
'c:\\apps\\svn\\bin\\svnlook.exe'

--
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Can webbrowser module get source code?

[Muddy Coder]

Hi All,

I played the demo of webbrowser module, with the code below:

import webbrowser
url = 'https://login.yahoo.com'
webbrowser.open_new_tab(url)

when I ran the code, it popped out a webpage nicely. I want to go
further: to get the source code of the webpage being displayed. Is it
possible to do it? I tried webbrow.get() but didn't work. Somebody can
help? Thanks!


Muddy Coder
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why is this invalid b = a += b ?

[Stef Mientki]

hello,

I can assign a value to more than 1 variable (name) in one line:

a = b = 3

So evaluation of this line must start at the right part.

But the following is not allowed:

b = 2
a = b += 1

I would think that if b has a value,
and the formula is evaluated from right to left,
there's nothing wrong with the above formula.

thanks
Stef Mientki
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Re: Regex for Python 2.7

[Gabriel Genellina]

En Sat, 24 Jan 2009 18:23:51 -0200, MRAB goo...@mrabarnett.plus.com  
escribió:



Some time ago I discovered this difference between regular expressions
in Python and Perl:

Python

\A matches at start of string
\Z matches at end of string

Perl

\A matches at start of string
\Z matches before terminal newline or at end of string
\z matches at end of string

In Perl \A == ^ and \Z == $ in single-string mode, but in Python \A == ^
and \Z != $ in single-string mode.


Why do you want the two to be equivalent? Isn't a good thing that you have  
both alternatives (\Z and $)? Use whichever is adequate in each case.


--
Gabriel Genellina

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Re: I'm a python addict !

[Terry Reedy]

Benjamin Kaplan wrote:



On Sat, Jan 24, 2009 at 5:35 PM, Lie Ryan lie.1...@gmail.com 
mailto:lie.1...@gmail.com wrote:


On Fri, 23 Jan 2009 19:58:09 -0700, Linuxguy123 wrote:

  I just started using python last week and I'm addicted.

you need to try this:

import antigravity

http://xkcd.com/353/


Just be careful with that. That guy was still floating 129 comics later 
(3 comics = 1 week). And still going Woo Python. You can see him 
floating near the peak of Mt. Everest.


http://xkcd.com/482/


For a Python 'program', see http://xkcd.com/534/

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Re: why is this invalid b = a += b ?

[MRAB]

Stef Mientki wrote:

hello,

I can assign a value to more than 1 variable (name) in one line:

a = b = 3

So evaluation of this line must start at the right part.

But the following is not allowed:

b = 2
a = b += 1

I would think that if b has a value, and the formula is evaluated
from right to left, there's nothing wrong with the above formula.


Assignment is a statement, not an expression. That's why:

if a = 0:
...

is illegal.

However, simple serial assignment such as:

a = b = 3

is useful enough to be supported as a special case.
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Re: Regex for Python 2.7

[MRAB]

Gabriel Genellina wrote:
 En Sat, 24 Jan 2009 18:23:51 -0200, MRAB goo...@mrabarnett.plus.com
 escribió:

 Some time ago I discovered this difference between regular expressions
 in Python and Perl:

 Python

 \A matches at start of string
 \Z matches at end of string

 Perl

 \A matches at start of string
 \Z matches before terminal newline or at end of string
 \z matches at end of string

 In Perl \A == ^ and \Z == $ in single-string mode, but in Python \A == ^
 and \Z != $ in single-string mode.

 Why do you want the two to be equivalent? Isn't a good thing that you
 have both alternatives (\Z and $)? Use whichever is adequate in each 
case.


Python's \Z is equivalent to Perl's \z, but there's no equivalent to 
Perl's \Z in multi-line mode.

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Re: I'm a python addict !

[MRAB]

Terry Reedy wrote:

Benjamin Kaplan wrote:



On Sat, Jan 24, 2009 at 5:35 PM, Lie Ryan lie.1...@gmail.com 
mailto:lie.1...@gmail.com wrote:


On Fri, 23 Jan 2009 19:58:09 -0700, Linuxguy123 wrote:

  I just started using python last week and I'm addicted.

you need to try this:

import antigravity

http://xkcd.com/353/


Just be careful with that. That guy was still floating 129 comics 
later (3 comics = 1 week). And still going Woo Python. You can see 
him floating near the peak of Mt. Everest.


http://xkcd.com/482/


For a Python 'program', see http://xkcd.com/534/


It doesn't follow PEP 8!
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Re: Is (-1 ==True) True or False? Neither

[Robert Kern]

On 2009-01-24 17:00, oktaysa...@superonline.com wrote:

Hi all,

I ran into a strange case.

Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit
(Intel)] on win32
...
  -1 == True
False
  -1 == False
False

This works though:
  if -1:
print OK

OK

After some head scratching, I realized that:
- bool is a subclass of int and that True and False evaluates to 1 and
0, so -1 is equal to neither; and
- The if -1: statement probably works by treating -1 as bool(-1).


Yes.


But I can't help finding the former comparison behavior odd. I admit
that it is odd to write such code but when someone writes -1 == True,
the intention is clearly a boolean comparison, not a numerical value
comparison, isn't it?


Not to me. The rules of Python state that the object on the left hand side is 
asked first how to compare the two values. Only if that fails is the object on 
the right hand side asked how to compare the objects.



As far as I understand, to do this comparison, python is casting
(loosely speaking) True to its numerical value, rather than casting -1
to its boolean value.


Not really. No casting goes on at all. bool is just one of the types that 
int.__eq__ knows how to handle because bool is a subclass of int. Vice-versa, 
bool.__eq__ knows how to handle ints, and it also does a numerical comparison; 
it never casts to a boolean.



So, my question is: wouldn't it make more sense to do just the opposite,
i.e. cast -1 to its boolean value and do a boolean comparison of the
operands, when one of the operands is True or False?

Or is this too fancy? What do you think?


I think that being explicit is better than being implicit. If you want to cast 
an object to a boolean, use bool() on it. Making special rules when comparing 
with booleans makes it harder to treat True and False as first-class objects.


--
Robert Kern

I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth.
  -- Umberto Eco

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Re: I'm a python addict !

[Robert Kern]

On 2009-01-23 22:25, Aahz wrote:

In articlemailman.7865.1232765899.3487.python-l...@python.org,
Linuxguy123linuxguy...@gmail.com  wrote:

I just started using python last week and I'm addicted.


Welcome!  Just be aware that excessive Perl-bashing is considered
somewhat tasteless on this newsgroup, but the occasional snide comment
should be fine.  ;-)


Or bash-bashing for that matter.  :-)

but-zsh-really-is-better'ly yrs,

--
Robert Kern

I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth.
  -- Umberto Eco

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Re: Can webbrowser module get source code?

[Benjamin Peterson]

Muddy Coder cosmo_general at yahoo.com writes:
 I want to go
 further: to get the source code of the webpage being displayed. Is it
 possible to do it? I tried webbrow.get() but didn't work. Somebody can
 help? Thanks!

To do this, you actually need to fetch the page yourself:

import urllib2
page_source = urllib2.urlopen(http://someaddress.com;).read()

 




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Re: RegEx issues

[John Machin]

On Jan 25, 5:59 am, Scott David Daniels scott.dani...@acm.org wrote:
 Sean Brown wrote:
  I have the following string ...:  td[ct] = [[ ... ]];\r\n
  The ... (representing text in the string) is what I'm extracting 
  So I think the regex \[\[(.*)\]\]; should do it.
  The problem is it appears that python is escaping the \ in the regex
  because I see this:
  reg = '\[\[(.*)\]\];'
  reg
  '\\[\\[(.*)\\]\\];'
  Now to me looks like it would match the string - \[\[ ... \]\];
  ...

 OK, you already have a good answer as to what is happening.
 I'll mention that raw strings were put in the language exactly for
 regex work.  They are useful for any time you need to use the backslash
 character (\) within a string (but not as the final character).
 For example:
      len(r'\a\b\c\d\e\f\g\h') == 16 and len('\a\b\c\d\e\f\g\h') == 13

 If you get in the habit of typing regex strings as r'...' or r...,
 and examining the patters with print(somestring), you'll ease your life.

All excellent suggestions, but I'm surprised that nobody has mentioned
the re.VERBOSE format.

Manual sez:
'''
re.X
re.VERBOSE
This flag allows you to write regular expressions that look nicer.
Whitespace within the pattern is ignored, except when in a character
class or preceded by an unescaped backslash, and, when a line contains
a '#' neither in a character class or preceded by an unescaped
backslash, all characters from the leftmost such '#' through the end
of the line are ignored.

That means that the two following regular expression objects that
match a decimal number are functionally equal:

a = re.compile(r\d +  # the integral part
   \.# the decimal point
   \d *  # some fractional digits, re.X)
b = re.compile(r\d+\.\d*)
'''

My comments:
(1)looks nicer is not the point; it's understandability
(2) if you need a space, use a character class -[ ]- not an
unescaped backslash -\ -
(3) the indentation in the manual doesn't fit my idea of looks
nicer; I'd do
a = re.compile(r
\d +  # the integral part
\.# the decimal point
\d *  # some fractional digits
, re.X)
(4) you can aid understandability by more indentation especially when
you have multiple capturing expressions and (?..) gizmoids e.g.
r
(
 . # prefix
)
(
 (?..) # look-back assertion
 (?) # etc etc
)

Worth a try if you find yourself going nuts getting the parentheses
matching.

Cheers,
John
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Re: why is this invalid b = a += b ?

[Terry Reedy]

Stef Mientki wrote:

hello,

I can assign a value to more than 1 variable (name) in one line:

a = b = 3

So evaluation of this line must start at the right part.

But the following is not allowed:

b = 2
a = b += 1


This strikes me as slightly incoherent.  Given that v op=exp is mostly 
that same as v = v op exp, I suppose you expect a = b += 1 to be mostly 
the same as a = b = b+1, but what would you do with a += b = 1, or even 
a *= b += 1.  There is some virtur to restricting augmented assignment 
to one target and one delimiter.  Even that seems to cause some trouble.


tjr

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Re: Possible to slice a string with unpacked tuple?

[Benjamin Peterson]

MRAB google at mrabarnett.plus.com writes:
 Does myString[myTuple[0] : myTuple[1]] count as unpacking? If it does, 
 then how about myString.__getslice__(*myTuple)?

Please don't use special method names directly and especially not
__getslice__(). It's deprecated and will be removed.




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Re: Regex for Python 2.7

[John Machin]

On Jan 25, 7:23 am, MRAB goo...@mrabarnett.plus.com wrote:
 Some time ago I discovered this difference between regular expressions
 in Python and Perl:

 Python

         \A matches at start of string
         \Z matches at end of string

 Perl

         \A matches at start of string
         \Z matches before terminal newline or at end of string
         \z matches at end of string

 In Perl \A == ^ and \Z == $ in single-string mode, but in Python \A == ^
 and \Z != $ in single-string mode.

 Obviously, changing Python's \Z to match Perl's could break existing
 code. \z could be added, but with the opposite meaning to Perl's:

         Python's \Z == Perl's \z
         Python's \z == Perl's \Z

 Would that be confusing?

 Any suggests welcome.

IIRC there was an exchange some years ago where the perl guy (Larry?)
admitted that he goofed and the consensus was that what Python had
done was better.
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Re: Parsing a string into a datetime object

[Mark.Petrovic]

On Jan 24, 10:56 am, Hrvoje Niksic hnik...@xemacs.org wrote:
 Mark.Petrovic mspetro...@gmail.com writes:
  Might someone comment on why %f is not accepted as a valid field
  directive in:

  from datetime import datetime
  created=2009-01-24 16:04:55.882788
  dt = datetime.strptime(created,%Y-%m-%d %H:%M:%S.%f)
  Traceback (most recent call last):
    File stdin, line 1, in module
    File /System/Library/Frameworks/Python.framework/Versions/2.5/lib/
  python2.5/_strptime.py, line 321, in strptime
      (bad_directive, format))
  ValueError: 'f' is a bad directive in format '%Y-%m-%d %H:%M:%S.%f'

  This is for Python 2.5.1 under OS X.

 time.strptime is documented to use the same set of directives as
 time.strftime, 
 andhttp://docs.python.org/library/time.html#time.strftimedoesn't mention
 a %f directive.

Thank you for the timely reply.

I guess I got mixed up by looking at the Python 2.6.1 docs, but used
the Python 2.5.1 interpreter:

http://docs.python.org/library/datetime.html

wherein datetime.html does show the availability of the %f directive
(if I'm reading all this correctly).
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