Re: execute sqlite3 dot commands in python

[Carl Banks]

On Feb 5, 3:19 pm, Steve Holden  wrote:
> gintare statkute wrote:
> > Does anybody know if it possible to execute sqlite3 dot commands in python?
>
> > dovanotas:/pages/links# python
> > Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26)
> > [GCC 4.3.2] on linux2
> > Type "help", "copyright", "credits" or "license" for more information.
>  import sqlite3
>  sqlite3  .help
> > Traceback (most recent call last):
> >   File "", line 1, in 
> > AttributeError: 'module' object has no attribute 'help'
>
> > the same with other commands:
> > .databases
> > .tables
> >http://www.sqlite.org/sqlite.html
>
> No.


Well actually you can, sort of.  For instance:

os.system('sqlite3 :memory: .help')


Carl Banks
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Re: PyQt4 designer custom properties - combo box style

[Andrew]

On Feb 4, 2:59 pm, David Boddie  wrote:
> On Tuesday 02 February 2010 22:25, Andrew wrote:
>
> > I am creating custom widgets for the PyQt4 Designer. I can create
> > custom properties, but I'm looking for how to create a custom property
> > that has a combo box drop down. I've seen them in the example widgets
> > and tried following them, but they are using pre-defined items to
> > populate their property, so it's not a very clear example of how to
> > get the combo box property to work.
>
> Can you explain a bit more about what you have seen and what you are
> trying to do. Are you trying to create a property that is treated
> specially by Designer or do you want to get the data for the combo
> box from somewhere else?

I'm attempting to create a drop down property for a custom widget I'm
creating. So when in designer and you scroll down to the custom
properties, under the regular widget properties, one of them would be
a drop down menu. The data to populate it will be coming from our API
and currently is a list of string-items. Yes, it would be treated
specially by Designer, since it's the only place it would be seen.

In the PyQt4\examples\designer folder, it carries a number of custom
widgets that will load into designer. The datetimeedit widget creates
a custom drop down menu property. The plugin pulls its information
from the QtCore libraries and from the QCalander Widget. Though I am
unable to find a better example or even explanation of how it's
actually creating that drop down menu.

>
> > Is there any other examples or help for this kind of setup?
>
> Have you seen this article?
>
>  http://qt.nokia.com/doc/qq/qq26-pyqtdesigner.html

No, I haven't, thanks. That might step in the right direction. I can't
run it right now, so I'm not sure if it is putting a spinbox as it's
property or just the value from the spin box.

>
> David

Andrew
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Re: method names nounVerb or verbNoun

[Carl Banks]

On Feb 5, 3:36 pm, Chris Rebert  wrote:
> On Fri, Feb 5, 2010 at 2:45 PM, Steven D'Aprano
>
>  wrote:
> > For instance, if getting or setting the voltage is an expensive
> > operation, you don't want to fool the user into thinking it is a cheap
> > attribute access.
>
> I strongly disagree with this rationale as it violates the Uniform
> Access Principle
> (http://en.wikipedia.org/wiki/Uniform_access_principle). Though I
> concede Python's builtins don't adhere to the UAP.

And I strongly disagree with the Uniform Access Principle.  I want my
accesses to an object to be explicitly "data-like" or "method-like",
even if

Based on the Wikipedia page, Meyer's main reason behind UAP seems to
be to minimize the need to break interfaces: the UAP is a means to an
end.  Python achieves that end without the conforming to UAP,
therefore it doesn't need it, and there's no reason to adhere to it.


Carl Banks
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Re: C:\Python25\Lib\IDLELIB\idle.pyw won't start

[Anthra Norell]

Gabriel,
  Thanks for your hints. I take them up one by one:

Gabriel Genellina wrote:

En Fri, 05 Feb 2010 10:23:57 -0300, Anthra Norell
 escribió:


   I upgraded from 2.4 to 2.5 and am unable to start an 2.5 idle
   window. The OS is Windows ME. The download of 2.5 finished with a
warning saying that 2.5 was the highest version for Windows 9* Any
tips?


I'd suggest a couple more tests.
Open the Python interpreter and execute:

py> from idlelib import idle

This *should* launch IDLE, or raise an error... 

>>> import idle
Traceback (most recent call last):
 File "", line 1, in 
 File "C:/PYTHON25/Lib/IDLELIB\idle.pyw", line 6, in 
   import PyShell
 File "C:\Python25\Lib\idlelib\PyShell.py", line 3, in 
ImportError: No module named os

>>> import os
Traceback (most recent call last):
 File "", line 1, in 
ImportError: No module named os



If nothing happens, exit
the process and open another one, and execute:

py> import Tkinter

>>> import Tkinter
Traceback (most recent call last):
 File "", line 1, in 
 File "C:\PYTHON25\lib\lib-tk\Tkinter.py", line 37, in 
   import FixTk # Attempt to configure Tcl/Tk without requiring PATH
 File "C:\PYTHON25\lib\lib-tk\FixTk.py", line 1, in 
   import sys, os
ImportError: No module named os



py> root = Tkinter.Tk()
py> root.mainloop()

An empty window should appear. If not, I'd say something is wrong with 
the

Tcl/Tk libraries.

For the time being 2.4 works fine. I'd much prefer 2.5, though, 
because it includes the image library (PIL), whereas 2.4 cannot even 
use it.


PIL has an impressive compatibility record - it works with *any* Python
version from 1.5.2 up. You should be able to use PIL with 2.4 without
problems.



Another good hint to a side issue: I should download PIL for P2.4. I 
guess it wasn't available back then and so I continued doing images with 
P2.2.


The real issue seems to be  a missing module "os".

C:\PYTHON25\LIB>dir os.*

Volume in drive C is PKBACK# 001
Volume Serial Number is 07D1-0103
Directory of C:\PYTHON25\Lib

OS   PY 25,211  08-03-06  9:27a OS.PY
OS   PYC24,430  06-05-08  6:45p OS.PYC
2 file(s) 49,641 bytes
0 dir(s)2,635.30 MB free

Here we are! Somehow the name got upper-cased! There's a whole bunch  
(131) of upper-cased names in the Lib I shall install the whole thing 
from scratch. That should take care if it. Thank you very much.


Frederic (Looking forward to Linux!)

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Re: how to run part of my python code as root

[Tomas Pelka]

sjdevn...@yahoo.com wrote:
> On Feb 4, 2:05 pm, Tomas Pelka  wrote:
>> -BEGIN PGP SIGNED MESSAGE-
>> Hash: SHA1
>>
>> Hey,
>>
>> is there possibility how to run part of my code (function for example)
>> as superuser.
>>
>> Or only way how to do this is create a wrapper and run is with Popen
>> through sudo (but I have to configure sudo to run "whole" python as root).
>

thank you for excellent explanation.

> In decreasing order of desirability:
> 1. Find a way to not need root access (e.g. grant another user or
> group access to whatever resource you're trying to access).
> 2. Isolate the stuff that needs root access into a small helper
> program that does strict validation of all input (including arguments,
> environment, etc); when needed, run that process under sudo or
> similar.

I thing this approach is the best for me. But how to connect two
separated processes, one running with root privileges and second without
superuser privileges? Is was thinking about Queues from multiprocessing,
didn't you know if it is a good choice?

> 2a. Have some sort of well-verified helper daemon that has access to
> the resource you need and mediates use of that resource.
> 3. Run the process as root, using seteuid() to switch between user and
> root privs.  The entire program must be heavily verified and do strict
> validation of all inputs.  Any attacker who gets control over the
> process can easily switch to root privs and do damage.  This is
> generally a bad idea.


-- 
Tom

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Doctests and decorated methods don't get along

[Steven D'Aprano]

It seems that doctest doesn't discover or execute doctests in methods 
which have been decorated.


Here is my test file:

# ==
class MyStaticMethod(object):
"""Emulate built-in staticmethod descriptor."""
def __init__(self, f):
self.f = f
def __get__(self, obj, objtype=None):
return self.f

class Test(object):
def method1(self):
"""Doc string

>>> print 'x'
x
"""

@staticmethod
def method2():
"""Doc string

>>> print 'y'
y
"""

@MyStaticMethod
def method3():
"""Doc string

>>> print '***'  # This test should fail.
z
"""

if __name__ == '__main__':
import doctest
doctest.testmod(verbose=True)
# ==


and here is the output using Python 2.6.4:

[st...@sylar python]$ python2.6 test_doctests.py
Trying:
print 'x'
Expecting:
x
ok
Trying:
print 'y'
Expecting:
y
ok
5 items had no tests:
__main__
__main__.MyStaticMethod
__main__.MyStaticMethod.__get__
__main__.MyStaticMethod.__init__
__main__.Test
2 items passed all tests:
   1 tests in __main__.Test.method1
   1 tests in __main__.Test.method2
2 tests in 7 items.
2 passed and 0 failed.
Test passed.


It doesn't even see method3, let alone run the tests.


This looks like  bug to me. Have I missed anything?

Any work arounds?



-- 
Steven
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Re: how to make a SimpleXMLRPCServer abort at CTRL-C under windows

[News123]

Hi Gabriel,



Gabriel Genellina wrote:
> En Fri, 05 Feb 2010 20:03:51 -0300, News123  escribió:
> 
>> I'm using an XMLRPC server under Windows.
>>
>> What I wonder is how I could create a server, that can be killed with
>> CTRL-C
>>
>> The server aborts easily with CTRL-BREAK but not with CTRL-C (under
>> Windows)
>>
>> If I press CTRL-C it will only abort when the next RPC call occurs.
>> It seems it is blocking in the select() call in the handle_request()
>> function.
> 
> Python 2.6 and up behaves exactly as you want.
> On previous versions you may use this:]



I', using python 2.6.4 nd neither on Win-XP nor on Win-7 I'm capable to
abort with CTR-C ?


On Linux however I can use CTRL-C .


> 
> class MyXMLRPCServer(SimpleXMLRPCServer.SimpleXMLRPCServer):
> 
> ... your methods ...
> 
> if not hasattr(SimpleXMLRPCServer.SimpleXMLRPCServer, 'shutdown'):
> 
> # pre 2.6
> quit = False
> 
> def serve_forever(self):
> while not self.quit:
> self.handle_request()
> 
> def shutdown(self):
> self.quit = True
> 
> def server_bind(self):
> self.socket.settimeout(1.0)
> SimpleXMLRPCServer.SimpleXMLRPCServer.server_bind(self)
> 


I tried something similiar, but without setting the socket timeout.
I'll try it now with.


N

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Re: "Nim" game being created, no GUI used... Need tips...

[Kev Dwyer]

On Fri, 05 Feb 2010 21:54:48 -0600, Jordan Uchima wrote:

Hello Jordan,

You could try something like this (not tested, and maybe I don't 
quite "get" the rules):

"""
Nim game.

In response to question on c.l.p.

"""

# Start with pot of thirteen pieces and two players.
# Each player takes 1 - 4 pieces each turn.
# Player who takes the last piece loses.


# Declare constants.
NUMBER_OF_PLAYERS = 2
TOTAL_PIECES_AT_START = 13

# Declare functions.

def rules():
"""Print the rules of the game."""
print 'Some rules'

def get_players():
"""Get the names of the players."""
# Let's put the player's names in a list.
players = []
# Looping like this saves us repeating lines of code for each player.
for player in range(NUMBER_OF_PLAYERS):
name = raw_input("Hello Player %d, what is your name?\n" % player)
players.append(player)
return players

def take_turn(player):
"""Handle a player's turn."""
# Turn logic goes here.
# Left as an exercise :)
the_remaining_number_of_pieces_after_this_turn = 1
return the_remaining_number_of_pieces_after_this_turn


def main():
"""Run the game."""
# Display the rules by calling rules function.
rules()
# Get the players by calling the get_players function.
players = get_players()
# Set up the game.
remaining_pieces = TOTAL_PIECES_AT_START
playing = True
# Main loop - let's play!
while playing:
# Take turns.
for player in players:
remaining_pieces = take_turn(player)
# Check if this player has lost.
if remaining_pieces == 0:
# Player has taken last piece.
print 'Sorry %s, you have lost.' % player
# Break out of the loop
playing = False
break


# Automatically run main function if we're run as a script.
if __name__ == '__main__':
main()

# End.

The "while" loop in the main function runs the game until a winner
(or loser in this case) is declared.  The "for" loop within the while 
loop handles the alternation of turns.  Have a look at the python 
tutorial at http://docs.python.org/tutorial/index.html for more on 
"while" and "for" statements.

Use functions to break up the code into related sections.  Check out 
the tutorial material for functions too.

This skeleton should give you a starting structure for your program.

Have fun :)

Kev


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Re: Exception class documentation

[Gerald Britton]

If you browse the Python source tree, you should be able to find it.

http://svn.python.org/view/python/trunk/Objects/exceptions.c?revision=77045&view=markup

On Fri, Feb 5, 2010 at 7:27 PM, Charles Yeomans  wrote:
>
> On Feb 5, 2010, at 2:13 PM, Gerald Britton wrote:
>
>> On Fri, Feb 5, 2010 at 12:55 PM, Charles Yeomans 
>> wrote:
>>>
>>> I am so far unable to find the information I want about the Exception
>>> class.
>>>  Information like the signature of __init__ seems to be unavailable.  Any
>>> suggestions where I might find such information?
>>>
>>
>> Though not documented, some silly tests indicate that it will accept
>> pretty much anything:
>>
> Exception(1,2,4,54)
>>
>> Exception(1, 2, 4, 54)
>
> Exception(*range(10))
>>
>> Exception(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
>
> Exception(*range(50))
>>
>> Exception(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
>> 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
>> 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
>
> Exception('a','b','c','d','e')
>>
>> Exception('a', 'b', 'c', 'd', 'e')
>
> Exception(Exception(1))
>>
>> Exception(Exception(1,),)
>
> I had also tried such tests.  If you pass a single argument msg, it is
> assigned to the message property, and the args property is set to (msg,). If
> you pass more than one argument, the tuple of arguments is assigned to the
> args property, and nothing is assigned to the message property.  I was
> hoping to at least find source code that provides a definitive answer.
>
>
> Charles Yeomans
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>



-- 
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Re: C:\Python25\Lib\IDLELIB\idle.pyw won't start

[Anthra Norell]

Gabriel,
  After reinstalling the whole package things are shaping up. It still 
doesn't work but it fails more to the point of your suggestions. I 
update the responses to your questions:


Anthra Norell wrote:

Gabriel,
  Thanks for your hints. I take them up one by one:

Gabriel Genellina wrote:

En Fri, 05 Feb 2010 10:23:57 -0300, Anthra Norell
 escribió:


   I upgraded from 2.4 to 2.5 and am unable to start an 2.5 idle
   window. The OS is Windows ME. The download of 2.5 finished with a
warning saying that 2.5 was the highest version for Windows 9* Any
tips?


I'd suggest a couple more tests.
Open the Python interpreter and execute:

py> from idlelib import idle

This *should* launch IDLE, or raise an error... 



>>> import idle
Traceback (most recent call last):
 File "", line 1, in 
 File "C:/PYTHON25/lib/IDLELIB\idle.py", line 19, in 
   PyShell.main()
 File "C:\Python25\Lib\idlelib\PyShell.py", line 1390, in main
   root = Tk(className="Idle")
 File "C:\PYTHON25\lib\lib-tk\Tkinter.py", line 1647, in __init__
   self.tk = _tkinter.create(screenName, baseName, className, 
interactive, want

objects, useTk, sync, use)
_tkinter.TclError: Can't find a usable init.tcl in the following 
directories:

   C:/PYTHON25/lib/tcl8.4 C:/lib/tcl8.4 C:/library

Checking for the whereabouts of the tcl8.4 directory  I find it in 
C:/PYTHON25/TCL together with a few more plus some files.


C:\PYTHON25\TCL>dir


Volume in drive C is PKBACK# 001
Volume Serial Number is 07D1-0103
Directory of C:\PYTHON25\TCL

.  11-25-08  4:09p .
.. 11-25-08  4:09p ..
TCL84LIB   191,802  03-27-06  4:23p tcl84.lib
TCLSTU~1 LIB 2,264  03-27-06  4:23p tclstub84.lib
DDE1 2 11-25-08  4:09p DDE1.2
REG1 1 11-25-08  4:09p REG1.1
TCL8 4 11-25-08  4:09p TCL8.4
TK8  4 11-25-08  4:09p TK8.4
TK84 LIB   167,288  03-27-06  4:44p tk84.lib
TKSTUB84 LIB 2,988  03-27-06  4:43p tkstub84.lib
TIX8 4 02-06-10  1:09p tix8.4
4 file(s)364,342 bytes
7 dir(s)2,569.25 MB free


This is the way the installer fixed it. The thing to do seems to be to 
move the tcl8.4 dirctory to the lib directory. Before I start upsetting 
things, perhaps you would know whether the whole TCL subtree should move.


Frederic

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Re: Google AI Challenge at U of Waterloo

[Man-wai Chang to The Door (24000bps)]

Hello, this is Jeff Cameron, the organizer of the Google AI Challenge.
I'm glad to see all this interest in our humble little contest. I wish
you all the best of luck, and encourage everyone to try their hand at
writing an AI for Tron! www.ai-contest.com


Someone please dumb the Tron ROM from the MAME32 project and use it as 
baseline answer. :)


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 / v \  Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (x86_64 Ubuntu 9.10)  Linux 2.6.32.7
  ^ ^   21:42:01 up 7 days 5:48 2 users load average: 0.00 0.02 0.00
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ANN: Resolver One 1.8 released

[Giles Thomas]

We're proud to announce that we've just released version 1.8 of
Resolver One.  This version switches to IronPython 2.6, which gives us
support for Python 2.6 syntax along with some serious performance
improvements.

Resolver One is a Windows-based spreadsheet that integrates Python
deeply into its recalculation loop, making the models you build more
reliable and more maintainable.

In version 1.8, we've worked hard on improving performance above and
beyond the gains we got from IronPython 2.6, and we've also added a
number of new statistical functions, along with various minor bugfixes
and smaller enhancements.

You can read more about Resolver One here:

  

We have a 31-day free trial version, so if you would like to take a
look, you can download it from our website:

  

If you want to use Resolver One in an Open Source project, we offer
free licenses for that:

  


Best regards,

Giles
--
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giles.tho...@resolversystems.com
+44 (0) 20 7253 6372

17a Clerkenwell Road, London EC1M 5RD, UK
VAT No.: GB 893 5643 79
Registered in England and Wales as company number 5467329.
Registered address: 843 Finchley Road, London NW11 8NA, UK
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ANN: PyGUI 2.2

[Greg Ewing]

PyGUI 2.2 is available:

  http://www.cosc.canterbury.ac.nz/greg.ewing/python_gui/

Highlights of this version:

  - TextEditor component with tabs, scrolling and word wrap

  - Classes for laying out components in rows, colums and grids

  - Printing support


What is PyGUI?
--

PyGUI is a cross-platform GUI toolkit designed to be lightweight
and have a highly Pythonic API.

--
Gregory Ewing
greg.ew...@canterbury.ac.nz
http://www.cosc.canterbury.ac.nz/greg.ewing/
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Re: Calendar GUI

[Sir Wilhelm the Sturdy]

On Feb 6, 12:59 am, Michael Torrie  wrote:
> Gabriel wrote:
> > On Fri, Feb 5, 2010 at 9:08 PM, William Gaggioli  
> > wrote:
> >> I'm working on setting up some software for a Peruvian non-profit to help
> >> them organize their incoming volunteers. One of the features I'd like to 
> >> add
> >> is acalendar-like view of the different volunteers arrival dates and
> >> staying time, with potentially some other info through some double-click
> >> action. Rather than writing acalendarguimyself, is there some open-source
> >>calendarprogram you guys could recommend that I could plug into? It has to
> >> be run locally, as the internet isn't so reliable down here, but other than
> >> that something simple and clean is ideal.
>
> > I wrote a gtkguifor googlecalendar.
>
> > Maybe you can adapt it to your needs.
>
> >http://code.google.com/p/googlecalendar-gtk/
>
> Would this work without an internet connection?  The original poster
> stated that internet isn't so reliable, hence the need for a local solution.

The functionality of Google calendar would be perfect, but it needs to
be run locally.
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Re: Exception class documentation

[Charles Yeomans]

On Feb 6, 2010, at 8:09 AM, Gerald Britton wrote:


If you browse the Python source tree, you should be able to find it.

http://svn.python.org/view/python/trunk/Objects/exceptions.c?revision=77045&view=markup




Perfect (even if I have to read C).  Thanks.

Charles Yeomans
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[RELEASED] Python 2.7 alpha 3

[Benjamin Peterson]

On behalf of the Python development team, I'm cheerful to announce the third
alpha release of Python 2.7.

Python 2.7 is scheduled (by Guido and Python-dev) to be the last major version
in the 2.x series.  Though more major releases have not been absolutely ruled
out, it's likely that the 2.7 release will an extended period of maintenance for
the 2.x series.

2.7 includes many features that were first released in Python 3.1.  The faster
io module, the new nested with statement syntax, improved float repr, set
literals, dictionary views, and the memoryview object have been backported from
3.1. Other features include an ordered dictionary implementation, unittests
improvements, a new sysconfig module, and support for ttk Tile in Tkinter.  For
a more extensive list of changes in 2.7, see
http://doc.python.org/dev/whatsnew/2.7.html or Misc/NEWS in the Python
distribution.

To download Python 2.7 visit:

 http://www.python.org/download/releases/2.7/

Please note that this is a development release, intended as a preview of new
features for the community, and is thus not suitable for production use.

The 2.7 documentation can be found at:

 http://docs.python.org/2.7

Please consider trying Python 2.7 with your code and reporting any bugs you may
notice to:

 http://bugs.python.org


Enjoy!

--
Benjamin Peterson
2.7 Release Manager
benjamin at python.org
(on behalf of the entire python-dev team and 2.7's contributors)
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determining which value is the first to appear five times in a list?

[Chris Colbert]

I'm working on a naive K-nearest-neighbors selection criteria for an optical
character recognition problem.

After I build my training set, I test each new image against against the
trained feature vectors and record the scores as follows:

match_vals = [(match_val_1, identifier_a), (match_val_2, identifier_b) 
] and so on..

then I sort the list so the smallest match_val's appear first (indictating a
strong match, so I may end up with something like this:

[(match_val_291, identifier_b), (match_val_23, identifier_b), (match_val_22,
identifer_k)  ]

Now, what I would like to do is step through this list and find the
identifier which appears first a K number of times.

Naively, I could make a dict and iterate through the list AND the dict at
the same time and keep a tally, breaking when the criteria is met.

such as:

def getnn(match_vals):
tallies = defaultdict(lambda: 0)
for match_val, ident in match_vals:
tallies[ident] += 1
for ident, tally in tallies.iteritems():
if tally == 5:
return ident

I would think there is a better way to do this. Any ideas?

Cheers!

Chris
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how to fix bugs (python)

[Shashwat Anand]

I am interested in fixing bugs in python. Are there entry-level bugs in
python which makes me familiarize with the process just like gnome have
gnome-love ? Just a small start-up guidance will be a big favour as I have
never fixed any.

Thanks,
~l0nwlf
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Re: determining which value is the first to appear five times in a list?

[Terry Reedy]

On 2/6/2010 1:24 PM, Chris Colbert wrote:

I'm working on a naive K-nearest-neighbors selection criteria for an
optical character recognition problem.

After I build my training set, I test each new image against against the
trained feature vectors and record the scores as follows:

match_vals = [(match_val_1, identifier_a), (match_val_2, identifier_b)
 ] and so on..

then I sort the list so the smallest match_val's appear first
(indictating a strong match, so I may end up with something like this:

[(match_val_291, identifier_b), (match_val_23, identifier_b),
(match_val_22, identifer_k)  ]

Now, what I would like to do is step through this list and find the
identifier which appears first a K number of times.

Naively, I could make a dict and iterate through the list AND the dict
at the same time and keep a tally, breaking when the criteria is met.

such as:

def getnn(match_vals):
 tallies = defaultdict(lambda: 0)
 for match_val, ident in match_vals:
 tallies[ident] += 1
 for ident, tally in tallies.iteritems():
 if tally == 5:
 return ident

I would think there is a better way to do this. Any ideas?


You only need to check that the incremented tally is 5, which is to say, 
that the about-to-be-incremented tally is 4.

t = tallies[ident]
if t < 4: tallies[ident] = t+1
else: return ident

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Re: python admin abuse complaint

[Ron Adam]

Xah Lee wrote:


For anyone reading this thread and interested in my opinions, i have
written many essays related to this and netiquette. Many of which
detail other similar incidences that i personally experienced, such as
freenode's irc ban in #emacs channel. If you are interested, they can
be found on my website, search for “ban xah lee”.


Xah,

Often (in the past) most of your posts have come across as complaints or 
ones pointing out problems or comparisons of the negative sort.  Your 
overall negative tone is just one of the reasons you get labeled a troll.


I suggest you try to be less confrontational and more positive.  Use your 
expertise and intelligence to help others but don't be offended if they 
don't agree with you.  There's more than one way to do almost everything 
and sometimes the best way for "a person" to do it is the way that person 
is able to grasp it.


Regards,
  Ron

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Re: Doctests and decorated methods don't get along

[John Posner]

On 2/6/2010 6:48 AM, Steven D'Aprano wrote:

class MyStaticMethod(object):
 """Emulate built-in staticmethod descriptor."""
 def __init__(self, f):
 self.f = f
 def __get__(self, obj, objtype=None):
 return self.f


How about using a function, instead of a class, to implement the decorator:

import functools
def MyStaticMethod(f):
@functools.wraps(f)
def _wrapper(*args, **kwargs):
return f(*args, **kwargs)
return _wrapper


For me, this produces the hoped-for doctest failure in 
__main__.Test.method3.


I tried making the class-based implementation work by using 
functools.wraps(), but I couldn't manage it. Also, doesn't the decorator 
protocol want the class to implement a __call__() method, not a 
__get__() method? Or am I getting hung up (not the first time) at the 
nexus of the descriptor and decorator protocols?


-John


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intolerant HTML parser

[Jim]

I generate some HTML and I want to include in my unit tests a check
for syntax.  So I am looking for a program that will complain at any
syntax irregularities.

I am familiar with Beautiful Soup (use it all the time) but it is
intended to cope with bad syntax.  I just tried feeding
HTMLParser.HTMLParser some HTML containing 'ab' and it
didn't complain.

That is, this:
h=HTMLParser.HTMLParser()
try:
h.feed('ab')
h.close()
print "I expect not to see this line"
except Exception, err:
print "exception:",str(err)
gives me "I expect not to see this line".

Am I using that routine incorrectly?  Is there a natural Python choice
for this job?

Thanks,
Jim
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Re: determining which value is the first to appear five times in a list?

[Wolodja Wentland]

On Sat, Feb 06, 2010 at 13:24 -0500, Chris Colbert wrote:
> [(match_val_291, identifier_b), (match_val_23, identifier_b), (match_val_22,
> identifer_k)  ]
> 
> Now, what I would like to do is step through this list and find the identifier
> which appears first a K number of times.

I think you can use the itertools.groupby(L, lambda el: el[1]) to group
elements in your *sorted* list L by the value el[1] (i.e. the
identifier) and then iterate through these groups until you find the
desired number of instances grouped by the same identifier.

Let me exemplify this:

>>> from itertools import groupby
>>> instances = [(1, 'b'), (2, 'b'), (3, 'a'), (4, 'c'), (5, 'c'), (6, 'c'), 
>>> (7, 'd')]
>>> k = 3
>>> grouped_by_identifier = groupby(instances, lambda el: el[1])
>>> grouped_by_identifier = ((identifier, list(group)) for identifier, group in 
>>> grouped_by_identifier)
>>> k_instances = (group for identifier, group in grouped_by_identifier if 
>>> len(group) == k)
>>> next(k_instances)
[(4, 'c'), (5, 'c'), (6, 'c')]
>>> next(k_instances)
Traceback (most recent call last):
  File "", line 1, in 
StopIteration

There are certainly millions of ways to do this and most of them will be
better than my proposal here, but you might like this approach. Another
approach would use itertools.takewhile() or itertools.ifilter() ... Just
have a look :-)

yours sincerely
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Re: intolerant HTML parser

[John Nagle]

Jim wrote:

I generate some HTML and I want to include in my unit tests a check
for syntax.  So I am looking for a program that will complain at any
syntax irregularities.

I am familiar with Beautiful Soup (use it all the time) but it is
intended to cope with bad syntax.  I just tried feeding
HTMLParser.HTMLParser some HTML containing 'ab' and it
didn't complain.


   Try HTML5lib.

http://code.google.com/p/html5lib/downloads/list

The syntax for HTML5 has well-defined notions of "correct",
"fixable", and "unparseable".  For example, the common but
incorrect form of HTML comments,

<- comment ->

is understood.

HTML5lib is slow, though.  Sometimes very slow.  It's really a reference 
implementation of the spec.  There's code like this:


#Should speed up this check somehow (e.g. move the set to a constant)
if ((0x0001 <= charAsInt <= 0x0008) or
(0x000E <= charAsInt <= 0x001F) or
(0x007F  <= charAsInt <= 0x009F) or
(0xFDD0  <= charAsInt <= 0xFDEF) or
charAsInt in frozenset([0x000B, 0xFFFE, 0x, 0x1FFFE,
0x1, 0x2FFFE, 0x2, 0x3FFFE,
0x3, 0x4FFFE, 0x4, 0x5FFFE,
0x5, 0x6FFFE, 0x6, 0x7FFFE,
0x7, 0x8FFFE, 0x8, 0x9FFFE,
0x9, 0xAFFFE, 0xA, 0xBFFFE,
0xB, 0xCFFFE, 0xC, 0xDFFFE,
0xD, 0xEFFFE, 0xE, 0xE,
0xF, 0x10FFFE, 0x10])):
self.tokenQueue.append({"type": tokenTypes["ParseError"],
"data":
 "illegal-codepoint-for-numeric-entity",
"datavars": {"charAsInt": charAsInt}})

Every time through the loop (once per character), they build that frozen
set again.


John Nagle
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Re: Doctests and decorated methods don't get along

[Terry Reedy]

On 2/6/2010 6:48 AM, Steven D'Aprano wrote:

It seems that doctest doesn't discover or execute doctests in methods
which have been decorated.


Here is my test file:

# ==
class MyStaticMethod(object):
 """Emulate built-in staticmethod descriptor."""
 def __init__(self, f):
 self.f = f
 def __get__(self, obj, objtype=None):
 return self.f

class Test(object):
 def method1(self):
 """Doc string

 >>>  print 'x'
 x
 """

 @staticmethod
 def method2():
 """Doc string

 >>>  print 'y'
 y
 """

 @MyStaticMethod
 def method3():
 """Doc string

 >>>  print '***'  # This test should fail.
 z
 """

if __name__ == '__main__':
 import doctest
 doctest.testmod(verbose=True)
# ==


and here is the output using Python 2.6.4:

[st...@sylar python]$ python2.6 test_doctests.py
Trying:
 print 'x'
Expecting:
 x
ok
Trying:
 print 'y'
Expecting:
 y
ok
5 items had no tests:
 __main__
 __main__.MyStaticMethod
 __main__.MyStaticMethod.__get__
 __main__.MyStaticMethod.__init__
 __main__.Test
2 items passed all tests:
1 tests in __main__.Test.method1
1 tests in __main__.Test.method2
2 tests in 7 items.
2 passed and 0 failed.
Test passed.


It doesn't even see method3, let alone run the tests.


Method3 is wrapped as an instance of MyStaticMethod and doctest does not 
see that as function. Even if it did, you would might have to copy the 
docstring (self.__doc__ = f.__doc__) to have the test run.


Note the following: (3.1)

>>> Test.method3

>>> Test.__dict__['method3']
<__main__.MyStaticMethod object at 0x00F5CDF0>
>>> Test.__dict__['method2']


Doctest has to scan the dict, so it does not see the attribute-lookup 
result.



This looks like  bug to me. Have I missed anything?


I would call it a limitation as I do not see the doc as promising 
otherwise. I believe doctest predates the descripter protocol, at least 
in its current form, so it may not be completely descriptor-aware. You 
certainly could file a feature request for improved recognition and 
subsequent calling of __get__. An initial patch would improve chances of 
action.


> Any workarounds?

Perhaps look at the doctest source to see why staticmethod instances are 
recognized as functions.


If doctest directly special-cases their recognition, then use the 
standard nested function approach for decorators, making sure to copy 
the doc string. Look at functools.wraps.


If doctest recognizes them by some characteristic that you have not 
emulated, try to improve that.


Terry Jan Reedy


Terry Jan Reedy

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Re: intolerant HTML parser

[Jim]

Thank you, John.  I did not find that by looking around; I must not
have used the right words.  The speed of the unit tests are not
critical so this seems like the solution for me.

Jim
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How to print all expressions that match a regular expression

[hzh...@gmail.com]

Hi,

I am a fresh man with python. I know there is regular expressions in
Python. What I need is that given a particular regular expression,
output all the matches. For example, given “[1|2|3]{2}” as the regular
expression, the program should output all 9 matches, i.e., "11 12 13
21 22 23 31 32 33".

Is there any well-written routine in Python or third-party program to
do this? If there isn't, could somebody make some suggestions on how
to write it myself?

Thanks.

Zhuo
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Re: determining which value is the first to appear five times in a list?

[Terry Reedy]

On 2/6/2010 2:09 PM, Wolodja Wentland wrote:

On Sat, Feb 06, 2010 at 13:24 -0500, Chris Colbert wrote:

[(match_val_291, identifier_b), (match_val_23, identifier_b), (match_val_22,
identifer_k)  ]

Now, what I would like to do is step through this list and find the identifier
which appears first a K number of times.


I think you can use the itertools.groupby(L, lambda el: el[1]) to group
elements in your *sorted* list L by the value el[1] (i.e. the
identifier) and then iterate through these groups until you find the
desired number of instances grouped by the same identifier.


This will generally not return the same result. It depends on whether OP 
wants *any* item appearing at least 5 times or whether the order is 
significant and the OP literally wants the first. Sorting the entire 
list may also take a *lot* longer.


Terry Jan Reedy

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Re: how to fix bugs (python)

[Terry Reedy]

On 2/6/2010 1:54 PM, Shashwat Anand wrote:

I am interested in fixing bugs in python. Are there entry-level bugs in
python which makes me familiarize with the process just like gnome have
gnome-love ? Just a small start-up guidance will be a big favour as I
have never fixed any.


Go to
python.org/dev/
and look at various pages there. The item tracker is at
bugs.python.org
Some items are marked easy. Many items have patches that need review. 
Help is needed both with Python code (modules) and C code (core and 
modules) depending on your abilities and interest. I would start with 
looking at current items on the tracker.


Terry Jan Reedy

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Re: how to fix bugs (python)

[Shashwat Anand]

Thanks Terry. I am looking on it. :)


On Sun, Feb 7, 2010 at 1:19 AM, Terry Reedy  wrote:

> On 2/6/2010 1:54 PM, Shashwat Anand wrote:
>
>> I am interested in fixing bugs in python. Are there entry-level bugs in
>> python which makes me familiarize with the process just like gnome have
>> gnome-love ? Just a small start-up guidance will be a big favour as I
>> have never fixed any.
>>
>
> Go to
> python.org/dev/
> and look at various pages there. The item tracker is at
> bugs.python.org
> Some items are marked easy. Many items have patches that need review. Help
> is needed both with Python code (modules) and C code (core and modules)
> depending on your abilities and interest. I would start with looking at
> current items on the tracker.
>
> Terry Jan Reedy
>
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>
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Subclassing datetime.date

[Sir Wilhelm the Sturdy]

Hi all,

I recently attempted to subclass the datetime.date object resulting in
horror and confusion, before submitting to a has-a relationship.
That's all fine and dandy, but out of curiosity I'd like to know what
I'm missing.

I was attempting to allow more flexible instancing of an object, like
so:

import datetime

class MyDate(datetime.date):

def __init__(self,*args,**kw):

if len(kw) + len(args) > 1:
self.construct(*args,**kw)

def construct(self,d,m=None,y=None,**kw):

today = datetime.date.today()
if m is None:
m = today.month
if y is None:
y = today.year

datetime.date.__init__(self,y,m,d,**kw)


However, it wasn't having the desired effect. Indeed, I could still
only instance it with 3 variables lest I get errors, and when I did
call it with 3 variables it didn't reflect the order change I had
implemented. Indeed, the properties were already set before it even
got to the construct method.

Is there some kind of built in I'm missing here?

Thanks all,
Will
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Re: determining which value is the first to appear five times in a list?

[Wolodja Wentland]

On Sat, Feb 06, 2010 at 14:42 -0500, Terry Reedy wrote:
> On 2/6/2010 2:09 PM, Wolodja Wentland wrote:

> >I think you can use the itertools.groupby(L, lambda el: el[1]) to group
> >elements in your *sorted* list L by the value el[1] (i.e. the
> >identifier) and then iterate through these groups until you find the
> >desired number of instances grouped by the same identifier.

> This will generally not return the same result. It depends on
> whether OP wants *any* item appearing at least 5 times or whether
> the order is significant and the OP literally wants the first.

Order is preserved by itertools.groupby - Have a look:

>>> instances = [(1, 'b'), (2, 'b'), (3, 'a'), (4, 'c'), (5, 'c'), (6, 'c'), 
>>> (7, 'b'), (8, 'b')]
>>> grouped_by_identifier = groupby(instances, lambda el: el[1])
>>> grouped_by_identifier = ((identifier, list(group)) for identifier, group in 
>>> grouped_by_identifier)
>>> k_instances = (group for identifier, group in grouped_by_identifier if 
>>> len(group) == 2)
>>> for group in k_instances:
... print group
... 
[(1, 'b'), (2, 'b')]
[(7, 'b'), (8, 'b')]

So the first element yielded by the k_instances generator will be the
first group of elements from the original list whose identifier appears
exactly k times in a row. 

> Sorting the entire list may also take a *lot* longer.
Than what? 

Am I missing something? Is the "*sorted*" the culprit? If yes -> Just
forget it as it is not relevant.
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Google AI Challenge at U of Waterloo

[Forthminder]

Contest runs from 4 February to 26 February 2010.

You may choose a programming language, such as
Java, C++, Python, Ruby or Haskell.

See details at

http://csclub.uwaterloo.ca/contest/problem_description.php

Bonne Chance!

Mentifex
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How Uninstall MatPlotLib?

[W. eWatson]

See Subject.
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Need installer recommendation

[Alan Biddle]

Hi,

I could use a recommendation on a free installer for use by an
unsophisticated programmer, that would be me, for some simple programs
which are a bit more than "Hello World," but only a little.  Basically
reading text files and processing the results.  Nothing fancy.  I am
using PY2EXE to create the distribution.

In doing the Google, and from past posting here, I see that most
recommendations are for inno and nsis.  I expect that either would do
what I want.  Is one a better choice for someone to learn enough to do
basic stuff without getting bogged down in details which are not
immediately important?


--
Alan
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Re: Building a multiline string

[Duncan Booth]

lallous  wrote:

> Now should I be using method 2 or 3 in production code?

Also Method1a:

# Method1a
x = ("line1" + # can use comments!
 "line2"+
 "line3")

Use Method1a or Method3 as you prefer: either of these generates a single 
string constant. Method2 is dumb.
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Re: Google AI Challenge at U of Waterloo

[Andrej Mitrovic]

Sweet, something to keep my brain busy for the next couple of weeks.
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Re: Google AI Challenge at U of Waterloo

[John Nagle]

Forthminder wrote:
...

Ignore.  Well-known nut. See "http://www.nothingisreal.com/mentifex_faq.html";

John Nagle
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Re: Google AI Challenge at U of Waterloo

[Jeff Cameron]

On Feb 5, 11:18 pm, "Man-wai Chang to The Door (24000bps)"
 wrote:
> On 06-Feb-10 08:02, Forthminder wrote:
>
> > Contest runs from 4 February to 26 February 2010.
> >http://csclub.uwaterloo.ca/contest/problem_description.php
> > Bonne Chance!
>
> It's definitely *not* exactly a programming challenge, but algorithm
> challenge.
>
> A programming (only) challenge should only require the players to write
> codes to implement an algorithm.
>
> This one requires both algorithm design & programming.
>
> --
>   �...@~@   Might, Courage, Vision, SINCERITY.
>   / v \  Simplicity is Beauty! May the Force and Farce be with you!
> /( _ )\ (x86_64 Ubuntu 9.10)  Linux 2.6.32.7
>    ^ ^   12:16:01 up 6 days 20:22 2 users load average: 0.45 0.26 0.09
> 不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 
> (CSSA):http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa

Hello, this is Jeff Cameron, the organizer of the Google AI Challenge.
I'm glad to see all this interest in our humble little contest. I wish
you all the best of luck, and encourage everyone to try their hand at
writing an AI for Tron! www.ai-contest.com
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Re: Google AI Challenge at U of Waterloo

[Paul Rubin]

"Man-wai Chang to The Door (24000bps)"  writes:
> It's definitely *not* exactly a programming challenge, but algorithm
> challenge.
> A programming (only) challenge should only require the players to
> write codes to implement an algorithm.

Eh?  Just about every interesting programming challenge is mostly about
algorithm selection.  Try some Project Euler for example.
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Re: Google AI Challenge at U of Waterloo

[Man-wai Chang to The Door (24000bps)]

Eh?  Just about every interesting programming challenge is mostly about
algorithm selection.  Try some Project Euler for example.


Everyone back then has abused the "programming" word to meant doing 
everything (algorithms (system analysis & design), data structures, 
coding, testing, documentation, auditing, ) at cheap 
salaries+benefits and tight schedules!


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/( _ )\ (x86_64 Ubuntu 9.10)  Linux 2.6.32.7
  ^ ^   21:40:01 up 7 days 5:46 2 users load average: 0.00 0.04 0.01
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
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Re: Passing command line argument to program from within IDLE?

[Alan Biddle]

Yes, that is what I was trying to do.  I need to puzzle a bit on the
solution, being a newbie.  Thanks!

--
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Re: Passing command line argument to program from within IDLE?

[Alan Biddle]

Terry,

CLICK, the light just came on.  Knowing that it is writable, I can
look at the length to determine whether there are any arguments.  If
not, I can switch to interactive input within the program, and input
the values that way.  A few easy extra lines.   Whatever works.
Thanks!!

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Re: Passing parameters in URL

[Diez B. Roggisch]

Am 04.02.10 01:42, schrieb John Bokma:

"Diez B. Roggisch"  writes:


Am 03.02.10 19:11, schrieb John Bokma:

Alan Harris-Reid   writes:


I have a web-page where each row in a grid has edit/delete buttons to
enable the user to maintain a selected record on another page.  The
buttons are in the form of a link with href='/item_edit?id=123', but
this string appears in the URL and gives clues as to how to bypass the
correct sequence of events, and could be risky if they entered the URL
directly (especially when it comes to deleting records).


You should *never* use a GET request to do actions like deleting
records. You already are aware of it being risky, so don't do this. You
should use GET for getting information, and POST for modifying information.


You should *never* say never, because there might be situations where
exceptions from rules are valid. This is one such cases. Making this a
post means that you need to resort to javascript to populate&  submit
a hidden HTML-form. Just for the sake of a POST.


Make each edit/delete button a submit button and optionally style it.


*slap* Yep, you are right, no JS needed. I should have thought about that.




Also, your claim of it being more risky is simply nonsense. GET is a
tiny bit more prone to tinkering by the average user. But calling this
less risky is promoting security by obscurity, at most.


Maybe you should think about what happens if someone posts:
http://example.com/item_delete?id=123";>  to a popular forum...


And the difference to posting

from urrlib2 import open
from urllib import encode

open("http://example.com/item_delete";, data=encode([("id", "123")]))

to that same public "hacker" forum is exactly what?

If your webapp happens to allow item_delete to be called without 
authentication & authorization, then *that's* your problem.


Diez
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Re: Passing parameters in URL

[Bruno Desthuilliers]

Diez B. Roggisch a écrit :

Am 03.02.10 19:11, schrieb John Bokma:

Alan Harris-Reid  writes:


I have a web-page where each row in a grid has edit/delete buttons to
enable the user to maintain a selected record on another page.  The
buttons are in the form of a link with href='/item_edit?id=123', but
this string appears in the URL and gives clues as to how to bypass the
correct sequence of events, and could be risky if they entered the URL
directly (especially when it comes to deleting records).


You should *never* use a GET request to do actions like deleting
records. You already are aware of it being risky, so don't do this. You
should use GET for getting information, and POST for modifying 
information.


You should *never* say never, because there might be situations where 
exceptions from rules are valid. This is one such cases.


Oh yes ?

Making this a 
post means that you need to resort to javascript to populate & submit a 
hidden HTML-form. 


I beg your pardon  This is total nonsense. Hopefully you don't need 
any js to emit a post request from a browser ! The only thing you need 
to do is to use a form and submit input instead.

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Re: Passing parameters in URL

[Bruno Desthuilliers]

Bruno Desthuilliers a écrit :

Diez B. Roggisch a écrit :

(snip)
Making this a post means that you need to resort to javascript to 
populate & submit a hidden HTML-form. 


I beg your pardon  This is total nonsense. 


Sorry, posted too fast, John alredy adressed this.
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Re: Stephen -- Bruce?

[Mensanator]

On Feb 4, 5:13 pm, "Alf P. Steinbach"  wrote:
> What's this about all the Stephen'ses here?
>
> Shouldn't it be Bruce?

Of course. We just call everyone Stephen to avoid confusion.

>
> - Alf (wondering)

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Re: Your beloved python features

[Bruce C. Baker]

"Terry Reedy"  wrote in message 
news:mailman.1929.1265328905.28905.python-l...@python.org...
> Iterators, and in particular, generators.
> A killer feature.
>
> Terry Jan Reedy
>

Neither unique to Python.

And then're the other killer "features" superfluous ":"s and rigid 
formatting! 


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Re: Your beloved python features

[Bruno Desthuilliers]

apeach a écrit :

I love intuitive type recognition.

no need to 'DIM everything AS Integer' etc.!



not to mention the ever hilarious (that is, when you don't have to 
maintain it) typical Java idiom:


   EveryThing theEveryThing = new EveryThing();

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Re: list.extend([]) Question

[Bruno Desthuilliers]

Gerald Britton a écrit :

I think it's because when you do ['a'].extend([]) or whatever, the
result is whatever the method "extend" returns.  But "extend" has no
return value


It does : it returns None.

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Stephen -- Bruce?

[Alf P. Steinbach]

What's this about all the Stephen'ses here?

Shouldn't it be Bruce?


- Alf (wondering)
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optparse print_help question

[mark.wendell]

Is there a way to use the optparser parser.print_help() so that it
ONLY prints out the options, and NOT the usage?

thanks
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TABS in the CPython C source code

[Alf P. Steinbach]

Just trying to delve into the CPython source code.

Pleasant surprise: while e.g. the gcc compiler is written in K&R C (1975 style 
C), CPython seems to be written in almost modern C (1989 and on).


But, hey, TABS used for indenting, combined haphazardly and randomly with SPACES 
used for indenting, in the same source files...


The size-8 tabs look really bad in an editor configured with tab size 4, as is 
common in Windows. I'm concluding that the CPython programmers configure their 
Visual Studio's to *nix convention. Or perhaps modern Visual Studio has default 
tab size 8, it wouldn't surprise me (the best version was the MSVC 6.0 Developer 
Studio, since then that IDE has only gone downhill being re-based on the Office 
Assistant inspired "for dummies" IDE that Microsoft had for web designers).


Anyways, I would suggest converting all those tabs to spaces, as e.g. the Boost 
library project does  --  no tabs allowed.


That's much more platform-independent. :-)


Cheers,

- Alf
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Re: PyQt4 designer custom properties - combo box style

[David Boddie]

On Saturday 06 February 2010 10:32, Andrew wrote:

> I'm attempting to create a drop down property for a custom widget I'm
> creating. So when in designer and you scroll down to the custom
> properties, under the regular widget properties, one of them would be
> a drop down menu. The data to populate it will be coming from our API
> and currently is a list of string-items. Yes, it would be treated
> specially by Designer, since it's the only place it would be seen.

Right. The drop down menus in the property editor usually contain values
defined for C++ enums which have been declared to Qt's meta-object system
when a C++ library or plugin is compiled. I'm not sure that PyQt can expose
lists of Python values in the same way.

An example of this is the alignment property in QLineEdit.

> In the PyQt4\examples\designer folder, it carries a number of custom
> widgets that will load into designer. The datetimeedit widget creates
> a custom drop down menu property. The plugin pulls its information
> from the QtCore libraries and from the QCalander Widget. Though I am
> unable to find a better example or even explanation of how it's
> actually creating that drop down menu.

Each of the individual properties are just single values, aren't they, not
collections of values?

>> Have you seen this article?
>>
>> http://qt.nokia.com/doc/qq/qq26-pyqtdesigner.html
> 
> No, I haven't, thanks. That might step in the right direction. I can't
> run it right now, so I'm not sure if it is putting a spinbox as it's
> property or just the value from the spin box.

The value from each spin box is turned into a property, so there are
latitude and longitude properties, though each of these only holds
a double precision floating point number. It sounds like you want to be
able to select from a list of values, or possibly change the values
themselves.

If it turns out you can't add a property to Qt Designer in the way you want,
you can still add a custom editor to the widget so that users can open a
context menu and select an item to configure it. This is similar to the way
you can open a dialog to edit the text inside QTextEdit widgets.

The article I referred to also covers this:

  http://qt.nokia.com/doc/qq/qq26-pyqtdesigner.html#makingamenu

David
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Re: Last M digits of expression A^N

[monkeys paw]

mukesh tiwari wrote:

Hello everyone. I am kind of new to python so pardon me if i sound
stupid.
I have to find out the last M digits of expression.One thing i can do
is (A**N)%M but my  A and N are too large (10^100) and M is less than
10^5. The other approach   was  repeated squaring and taking mod of
expression. Is there any other way to do this in python more faster
than log N.


How do you arrive at log N as the performance number?



def power(A,N,M):
ret=1
while(N):
if(N%2!=0):ret=(ret*A)%M
A=(A*A)%M
N=N//2
return ret

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Re: TABS in the CPython C source code

[Andrej Mitrovic]

On Feb 6, 9:31 pm, "Alf P. Steinbach"  wrote:
> Just trying to delve into the CPython source code.
>
> Pleasant surprise: while e.g. the gcc compiler is written in K&R C (1975 style
> C), CPython seems to be written in almost modern C (1989 and on).
>
> But, hey, TABS used for indenting, combined haphazardly and randomly with 
> SPACES
> used for indenting, in the same source files...
>
> The size-8 tabs look really bad in an editor configured with tab size 4, as is
> common in Windows. I'm concluding that the CPython programmers configure their
> Visual Studio's to *nix convention. Or perhaps modern Visual Studio has 
> default
> tab size 8, it wouldn't surprise me (the best version was the MSVC 6.0 
> Developer
> Studio, since then that IDE has only gone downhill being re-based on the 
> Office
> Assistant inspired "for dummies" IDE that Microsoft had for web designers).
>
> Anyways, I would suggest converting all those tabs to spaces, as e.g. the 
> Boost
> library project does  --  no tabs allowed.
>
> That's much more platform-independent. :-)
>
> Cheers,
>
> - Alf

So what's stopping you from doing this yourself?
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Re: TABS in the CPython C source code

[Alf P. Steinbach]

* Andrej Mitrovic:

On Feb 6, 9:31 pm, "Alf P. Steinbach"  wrote:

Just trying to delve into the CPython source code.

Pleasant surprise: while e.g. the gcc compiler is written in K&R C (1975 style
C), CPython seems to be written in almost modern C (1989 and on).

But, hey, TABS used for indenting, combined haphazardly and randomly with SPACES
used for indenting, in the same source files...

The size-8 tabs look really bad in an editor configured with tab size 4, as is
common in Windows. I'm concluding that the CPython programmers configure their
Visual Studio's to *nix convention. Or perhaps modern Visual Studio has default
tab size 8, it wouldn't surprise me (the best version was the MSVC 6.0 Developer
Studio, since then that IDE has only gone downhill being re-based on the Office
Assistant inspired "for dummies" IDE that Microsoft had for web designers).

Anyways, I would suggest converting all those tabs to spaces, as e.g. the Boost
library project does  --  no tabs allowed.

That's much more platform-independent. :-)

Cheers,

- Alf


So what's stopping you from doing this yourself?


Depends what "this" you're referring to.

If by "this" you mean, automatically converting tabs to spaces on checking out a 
newer version of a CPython source file, nothing in particular stops anyone from 
doing that. But it's needless work, and it results in "false positive" changes 
when checking in something. That's why e.g. Boost standardizes on spaces.


If by "this" you mean, changing the coding guidelines (if such exist) for the 
CPython project, well I'm not involved, so the best I can do is to float the 
idea and point to existing practice in other projects, which I've now done. :-)



Cheers & hth.,

- Alf
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Re: TABS in the CPython C source code

[Neil Hodgson]

Alf P. Steinbach:

> The size-8 tabs look really bad in an editor configured with tab size 4,
> as is common in Windows. I'm concluding that the CPython programmers
> configure their Visual Studio's to *nix convention.

   Most of the core developers use Unix.

> Anyways, I would suggest converting all those tabs to spaces, as e.g.
> the Boost library project does  --  no tabs allowed.

   This would damage the usefulness of source control histories (svn
annotate) as all of the converted lines would show this recent cosmetic
change rather than the previous change which is likely to be a
substantive modification.

   Neil
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Re: Subclassing datetime.date

[John Bokma]

Sir Wilhelm the Sturdy  writes:

F> Hi all,
>
> I recently attempted to subclass the datetime.date object resulting in
> horror and confusion, before submitting to a has-a relationship.
> That's all fine and dandy, but out of curiosity I'd like to know what
> I'm missing.
>
> I was attempting to allow more flexible instancing of an object, like
> so:
>
> import datetime
>
> class MyDate(datetime.date):
>
> def __init__(self,*args,**kw):
>
> if len(kw) + len(args) > 1:
> self.construct(*args,**kw)
>
> def construct(self,d,m=None,y=None,**kw):
>
> today = datetime.date.today()
> if m is None:
> m = today.month
> if y is None:
> y = today.year
>
> datetime.date.__init__(self,y,m,d,**kw)
>
>
> However, it wasn't having the desired effect. Indeed, I could still
> only instance it with 3 variables lest I get errors, and when I did
> call it with 3 variables it didn't reflect the order change I had
> implemented. Indeed, the properties were already set before it even
> got to the construct method.

__init__ is *not* the construction method, __new__ is (at least with new
style classes)

> Is there some kind of built in I'm missing here?

I guess __new__ but I am quite the newbie.

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http://castleamber.com/ - Perl & Python Development
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Re: TABS in the CPython C source code

[John Bokma]

"Alf P. Steinbach"  writes:

> Just trying to delve into the CPython source code.
>
> Pleasant surprise: while e.g. the gcc compiler is written in K&R C
> (1975 style C), CPython seems to be written in almost modern C (1989
> and on).
>
> But, hey, TABS used for indenting, combined haphazardly and randomly
> with SPACES used for indenting, in the same source files...
>
> The size-8 tabs look really bad in an editor configured with tab size
> 4, as is common in Windows.

Then you are either used a broken editor or a misconfigured editor. I've
used TextPad for ages, and it can be configured to hard tab 8 (might
even be the default [1]).


[1] With Perl coding I configured it to indent 4 spaces, hard tab 4
spaces and convert hard tabs to 4 spaces while saving, so no surprises.
-- 
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http://castleamber.com/ - Perl & Python Development
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how to add pydoc strings to 'Data and other attributes'

[News123]

I'm having some problems with pydoc and I was not very sucessful in
googling. (probably missng one key word)

Is there soemthing like a documentation of pydoc (execpt pydocs output
of pydoc,  which doesn't seem to answer my question )

I can add docstrings to
- the file head
- to a class
- to a class function
- to a property

but I don't know how document a class attribute (like 'name' ) in my
example below


Does anybody know how to doc it?

# file starts here

#
#
# This appears in the python documentation
#
#

__author__ = 'News123' # this will also be part of pydoc

""" general blabla will not be part of pydoc"""

class MyClass(object):
""" This class can be doc-ed """

name = 3 ### I don't know how to document this

def get_f(self):
""" the function get_f is here """
return 3

f = property(get_f,doc="this property is also documented")

# file ends here


thanks for any help


N
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Re: Code snippet: dualmethod descriptor

[Arnaud Delobelle]

Steven D'Aprano  writes:

> On Thu, 04 Feb 2010 00:09:02 -0300, Gabriel Genellina wrote:
>
>> En Sat, 30 Jan 2010 03:06:18 -0300, Steven D'Aprano
>>  escribió:
>> 
>>> class dualmethod(object):
> [...]
>
>> Seems useful!
>> Perhaps a better place to post it would be
>> , at least it's
>> easier to search.
>
>
>
> Thank you for the encouragement. The recipe is now posted:
>
> http://code.activestate.com/recipes/577030/

Oddly, in Python 3 you can achieve something a bit similar very simply:

>>> class A:
... def foo(self=None):
... return "Instance" if self else "Class"
... 
>>> A.foo()
'Class'
>>> a = A()
>>> a.foo()
'Instance'

It works in python 3 because unbound methods are plain functions.

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Re: Dreaming of new generation IDE

[Arnaud Delobelle]

"Gabriel Genellina"  writes:

> En Fri, 05 Feb 2010 19:22:39 -0300, bartc  escribió:
>> "Steve Holden"  wrote in message
>> news:mailman.1998.1265399766.28905.python-l...@python.org...
>>> Arnaud Delobelle wrote:
 Robert Kern  writes:

> I prefer Guido's formulation (which, naturally, I can't find a direct
> quote for right now): if you expect that a boolean argument is only
> going to take *literal* True or False, then it should be split into
>  ^^^
> two functions.

 So rather than three boolean arguments, would you have eight functions?

>>> If there's genuinely a need for that functionality, yes.
>>
>> So you want a function such as drawtext(s, bold=true, italic=false,
>> underline=true) to be split into:
>>
>> drawtext(s)
>> drawtextb(s)
>> drawtexti(s)
>> drawtextu(s)
>> drawtextbi(s)
>> drawtextbu(s)
>> drawtextiu(s)
>> drawtextbiu(s)
>
> Note the *literal* part. If you (the programmer) is likely to know the
> parameter value when writing the code, then the function is actually two
> separate functions.

Thanks, I understand what Steve Holden meant now.

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Re: How to print all expressions that match a regular expression

[Roy Smith]

In article 
,
 "hzh...@gmail.com"  wrote:

> Hi,
> 
> I am a fresh man with python. I know there is regular expressions in
> Python. What I need is that given a particular regular expression,
> output all the matches. For example, given ³[1|2|3]{2}² as the regular
> expression, the program should output all 9 matches, i.e., "11 12 13
> 21 22 23 31 32 33".
> 
> Is there any well-written routine in Python or third-party program to
> do this? If there isn't, could somebody make some suggestions on how
> to write it myself?
> 
> Thanks.
> 
> Zhuo

Please enumerate all the strings which match ".*".  Use additional sheets 
of paper if needed.
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Re: TABS in the CPython C source code

[Benjamin Peterson]

Neil Hodgson  gmail.com> writes:
>This would damage the usefulness of source control histories (svn
> annotate) as all of the converted lines would show this recent cosmetic
> change rather than the previous change which is likely to be a
> substantive modification.

That's not completely true given svn diff -x -w.




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Re: Last M digits of expression A^N

[Shashwat Anand]

Yes, it can be done. Have a look at :
http://en.wikipedia.org/wiki/Modular_exponentiation
The algorithm is also mentioned in CLRS.I tried writing my own
modular-exponentiation code following CLRS but observed that python pow()
function is much more efficient.
Have a look at this problem : https://www.spoj.pl/problems/LASTDIG/
as you can see ( https://www.spoj.pl/status/LASTDIG,l0nwlf/ )my first
solution used algorithm hard-coded from CLRS which took 0.04 sec however
using pow() function directly improved the efficiency to 0.0 So I would
suggest to go for pow() unless you intend to learn modular exponentiation
algorithm for which hand-coding is a must.

here are my solutions :
first one (hand-coded):


   1. def pow(a, b):
   2. if( not b):
   3.return 1
   4. if( b & 1 ):
   5.return ( pow( a, b - 1 ) * a ) % 10
   6.
   7. tmp = pow( a, b / 2 )
   8. return ( tmp * tmp ) % 10;
   9.
   10. for i in xrange(input()):
   11.  a,b = [ int(x) for x in raw_input().split(' ')]
   12.  print( pow( a % 10, b ) )


second one (pow()):


   1. for i in range(int(raw_input())):
   2. a,b = [int(x) for x in raw_input().split()]
   3. print pow (a,b,10)
   4.


HTH
~l0nwlf

On Sun, Feb 7, 2010 at 2:32 AM, monkeys paw  wrote:

> mukesh tiwari wrote:
>
>> Hello everyone. I am kind of new to python so pardon me if i sound
>> stupid.
>> I have to find out the last M digits of expression.One thing i can do
>> is (A**N)%M but my  A and N are too large (10^100) and M is less than
>> 10^5. The other approach   was  repeated squaring and taking mod of
>> expression. Is there any other way to do this in python more faster
>> than log N.
>>
>
> How do you arrive at log N as the performance number?
>
>
>
>> def power(A,N,M):
>>ret=1
>>while(N):
>>if(N%2!=0):ret=(ret*A)%M
>>A=(A*A)%M
>>N=N//2
>>return ret
>>
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>
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Re: TABS in the CPython C source code

[Benjamin Peterson]

Alf P. Steinbach  start.no> writes:

> Anyways, I would suggest converting all those tabs to spaces

This has been discussed to death of Python-dev. We use spaces for all new files
and tabs for historical reasons in old files. Mixed ones should be converted one
way or the other.

> 
> That's much more platform-independent. 




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Re: Last M digits of expression A^N

[Shashwat Anand]

a nice exercise to do can be this problem :
http://www.codechef.com/MARCH09/problems/A4/ , it deals with both cases,
first and last k digits and can be performed within O(log n)

On Sun, Feb 7, 2010 at 3:58 AM, Shashwat Anand wrote:

> Yes, it can be done. Have a look at :
> http://en.wikipedia.org/wiki/Modular_exponentiation
> The algorithm is also mentioned in CLRS.I tried writing my own
> modular-exponentiation code following CLRS but observed that python pow()
> function is much more efficient.
> Have a look at this problem : https://www.spoj.pl/problems/LASTDIG/
> as you can see ( https://www.spoj.pl/status/LASTDIG,l0nwlf/ )my first
> solution used algorithm hard-coded from CLRS which took 0.04 sec however
> using pow() function directly improved the efficiency to 0.0 So I would
> suggest to go for pow() unless you intend to learn modular exponentiation
> algorithm for which hand-coding is a must.
>
> here are my solutions :
> first one (hand-coded):
>
>
>1. def pow(a, b):
>2. if( not b):
>3.  return 1
>4. if( b & 1 ):
>5.  return ( pow( a, b - 1 ) * a ) % 10
>
>6.
>7. tmp = pow( a, b / 2 )
>8. return ( tmp * tmp ) % 10;
>9.
>10. for i in xrange(input()):
>11.  a,b = [ int(x) for x in raw_input().split(' ')]
>
>12.  print( pow( a % 10, b ) )
>
>
> second one (pow()):
>
>
>1. for i in range(int(raw_input())):
>
>2. a,b = [int(x) for x in raw_input().split()]
>
>3. print pow (a,b,10)
>4.
>
>
> HTH
> ~l0nwlf
>
>
> On Sun, Feb 7, 2010 at 2:32 AM, monkeys paw  wrote:
>
>> mukesh tiwari wrote:
>>
>>> Hello everyone. I am kind of new to python so pardon me if i sound
>>> stupid.
>>> I have to find out the last M digits of expression.One thing i can do
>>> is (A**N)%M but my  A and N are too large (10^100) and M is less than
>>> 10^5. The other approach   was  repeated squaring and taking mod of
>>> expression. Is there any other way to do this in python more faster
>>> than log N.
>>>
>>
>> How do you arrive at log N as the performance number?
>>
>>
>>
>>> def power(A,N,M):
>>>ret=1
>>>while(N):
>>>if(N%2!=0):ret=(ret*A)%M
>>>A=(A*A)%M
>>>N=N//2
>>>return ret
>>>
>> --
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>>
>
>
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Re: determining which value is the first to appear five times in a list?

[Terry Reedy]

On 2/6/2010 3:25 PM, Wolodja Wentland wrote:

On Sat, Feb 06, 2010 at 14:42 -0500, Terry Reedy wrote:

On 2/6/2010 2:09 PM, Wolodja Wentland wrote:



I think you can use the itertools.groupby(L, lambda el: el[1]) to group
elements in your *sorted* list L by the value el[1] (i.e. the
identifier) and then iterate through these groups until you find the
desired number of instances grouped by the same identifier.



This will generally not return the same result. It depends on
whether OP wants *any* item appearing at least 5 times or whether
the order is significant and the OP literally wants the first.


Order is preserved by itertools.groupby - Have a look:


Sorting does not.



instances = [(1, 'b'), (2, 'b'), (3, 'a'), (4, 'c'), (5, 'c'), (6, 'c'), (7, 
'b'), (8, 'b')]
grouped_by_identifier = groupby(instances, lambda el: el[1])
grouped_by_identifier = ((identifier, list(group)) for identifier, group in 
grouped_by_identifier)
k_instances = (group for identifier, group in grouped_by_identifier if 
len(group) == 2)
for group in k_instances:

... print group
...
[(1, 'b'), (2, 'b')]
[(7, 'b'), (8, 'b')]

So the first element yielded by the k_instances generator will be the
first group of elements from the original list whose identifier appears
exactly k times in a row.


Sorting the entire list may also take a *lot* longer.

Than what?


Than linearly scanning for the first 5x item, as in my corrected version 
of the original code.


Terry Jan Reedy

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Re: How to print all expressions that match a regular expression

[Ben Finney]

Roy Smith  writes:

>  "hzh...@gmail.com"  wrote:
> > What I need is that given a particular regular expression, output
> > all the matches.
[…]

> Please enumerate all the strings which match ".*". Use additional
> sheets of paper if needed.

+1 QOTW

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_o__)   and The Brain_ |
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new.instancemethod __iter__

[Martin Drautzburg]

Hello all

When I create an Object and set its __iter__ method from outside

s = Sequence #one of my own classes
s.__iter__ = new.instancemethod(f,s,Sequence)

I get different results, depending on whether I call


for x in y.__iter__():
print x

or

for x in y:
print x

The first case does what I expected, i.e. it iterates over whatever f()
yields. In the second case nothing is printed. I have the impression
that it still calls the original __iter__() method (the one defined at
the class level).

Why is that so?
How can I replace the __iter__() method so it does what I want.

The reason I want to do such things is I need to implement operations
similar to what itertools do. However I want my own classes and the
operations are only similar to itertools, but differ in significant
details.
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Re: Last M digits of expression A^N

[Dave Angel]

monkeys paw wrote:
mukesh 
tiwari wrote:

Hello everyone. I am kind of new to python so pardon me if i sound
stupid.
I have to find out the last M digits of expression.One thing i can do
is (A**N)%M but my  A and N are too large (10^100) and M is less than
10^5. The other approach   was  repeated squaring and taking mod of
expression. Is there any other way to do this in python more faster
than log N.


How do you arrive at log N as the performance number?



def power(A,N,M):
ret=1
while(N):
if(N%2!=0):ret=(ret*A)%M
A=(A*A)%M
N=N//2
return ret


Because the N= N/2 operation in the loop means that the number of loops 
is equal to the number of  bits in N, or the log-base-2 of N.


DaveA
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Re: Doctests and decorated methods don't get along

[Steven D'Aprano]

On Sat, 06 Feb 2010 14:00:28 -0500, John Posner wrote:

> On 2/6/2010 6:48 AM, Steven D'Aprano wrote:
>> class MyStaticMethod(object):
>>  """Emulate built-in staticmethod descriptor.""" 
>>  def __init__(self, f):
>>  self.f = f
>>  def __get__(self, obj, objtype=None):
>>  return self.f
> 
> How about using a function, instead of a class, to implement the
> decorator:

I've had problems with function decorators and doctest in the past. If I 
remember the problem correctly, functools.wraps changing the __module__ 
of the wrapped function, making it look like it came from the functool 
module, and so doctest would not run the tests. But it seems that has 
been fixed in 2.6: I can confirm your version works as expected.

Nevertheless, I think it is a limitation of doctest that it doesn't see 
methods using the descriptor protocol. Even if I could work around my 
immediate issue by using a function decorator (and I don't think I can) 
I'd still want to fix this problem.


> I tried making the class-based implementation work by using
> functools.wraps(), but I couldn't manage it. 

Me neither. I think the problem is that the doctest.DocTestFinder class 
doesn't find descriptor-based methods. It special cases staticmethod, 
classmethod and property.



> Also, doesn't the decorator
> protocol want the class to implement a __call__() method, not a
> __get__() method? Or am I getting hung up (not the first time) at the
> nexus of the descriptor and decorator protocols?

In this case, I'm actually using a descriptor as the decorator.

The descriptor is called at attribute lookup, before the method is 
called. __get__ returns a function, which has a __call__ method, and it 
should all just work.



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Re: TABS in the CPython C source code

[Antoine Pitrou]

Le Sat, 06 Feb 2010 22:26:55 +, Benjamin Peterson a écrit :
> Neil Hodgson  gmail.com> writes:
>>This would damage the usefulness of source control histories (svn
>> annotate) as all of the converted lines would show this recent cosmetic
>> change rather than the previous change which is likely to be a
>> substantive modification.
> 
> That's not completely true given svn diff -x -w.

That's even less true given we aren't ashamed to make other kinds of 
cosmetic changes when desired, even though it also "damages the 
usefulness of source control histories" ;-)


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Re: new.instancemethod __iter__

[Steven D'Aprano]

On Sat, 06 Feb 2010 23:53:53 +0100, Martin Drautzburg wrote:

> Hello all
> 
> When I create an Object and set its __iter__ method from outside
> 
> s = Sequence #one of my own classes
> s.__iter__ = new.instancemethod(f,s,Sequence)

I'm confused as to why you are aliasing your class before changing it. 
The above just makes s an alternative name for Sequence.

Did you mean this?

s = Sequence() # make an instance of the class


> I get different results, depending on whether I call
> 
> 
> for x in y.__iter__():
> print x

What's y? Where does it come from? Is y supposed to be an instance of 
Sequence?


> or
> 
> for x in y:
> print x
> 
> The first case does what I expected, i.e. it iterates over whatever f()
> yields. In the second case nothing is printed. I have the impression
> that it still calls the original __iter__() method (the one defined at
> the class level).

Yes, that's almost certainly what is happening. As an optimization, 
Python bypasses the instance for special methods __NAME__.


> Why is that so?
> How can I replace the __iter__() method so it does what I want.

The best solution is, find another way to do what you want.

The clunky solution is to use delegation to wrap your class, and have the 
outer class re-direct calls to special methods to the instance first.

 
> The reason I want to do such things is I need to implement operations
> similar to what itertools do. However I want my own classes and the
> operations are only similar to itertools, but differ in significant
> details.

I don't understand this.

If you want iterator operations "similar to itertools", why does this 
mean you need to replace anything? Just create your own iterators.

Or use pre-processing and post-processing to get what you want.

Can you show an example of what you would like to happen?



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Re: merge stdin, stdout?

[jonny lowe]

On Feb 5, 11:10 pm, "Gabriel Genellina" 
wrote:
> En Fri, 05 Feb 2010 17:39:07 -0300, jonny lowe
>  escribió:
>
>
>
>
>
> > On Feb 4, 8:20 pm, exar...@twistedmatrix.com wrote:
> >> On 01:56 am, jonny.lowe.12...@gmail.com wrote:
> >> >What I want is to have an easy way tomergeinput.txt and thestdout
> >> >so that output.txt look like:
>
> >> >Enter a number: 42
> >> >You entered 42.
>
> >> >Here, the first 42 is of course from input.txt.
>
> >> It sounds like you might be looking forscript(1)?
>
> > $ script -c "./y < input.txt" output.txt
> > Script started, file is output.txt
> > gimme x:you entered hello
> > Script done, file is output.txt
>
> Try moving the redirection out of the command:
>
> $ script -c ./y output.txt < input.txt
>
> --
> Gabriel Genellina- Hide quoted text -
>
> - Show quoted text -

The result is the same as before. I've tested in fedora11.

-jon
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Re: Last M digits of expression A^N

[Mark Dickinson]

On Feb 5, 8:14 pm, mukesh tiwari  wrote:
> I have to find out the last M digits of expression.One thing i can do
> is (A**N)%M but my  A and N are too large (10^100) and M is less than
> 10^5. The other approach   was  repeated squaring and taking mod of
> expression. Is there any other way to do this in python more faster
> than log N.

By the way, given that your M is fairly tiny compared with A and N, a
little bit of elementary number theory (e.g., Euler's theorem) could
save you a lot of time here.  For example,

pow(a, n, 10**5)

is equivalent to

pow(a, 5 + (n - 5) % 4, 10**5)

for any n >= 5.  Not sure if this is the kind of thing you're looking
for.

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Re: new.instancemethod __iter__

[Christian Heimes]

Martin Drautzburg wrote:
> The first case does what I expected, i.e. it iterates over whatever f()
> yields. In the second case nothing is printed. I have the impression
> that it still calls the original __iter__() method (the one defined at
> the class level).
>
> Why is that so?
> How can I replace the __iter__() method so it does what I want.

Virtually all __magic__ methods are looked up on the type, not the
instance. So obj.__iter__() translates into type(obj).__iter__(obj).

If you *really* need to overwrite __iter__ on your instance rather than
defining it on your class, you need to proxy the method call:

class MyObject(object):
   def __iter__(self):
  return self.myiter()

obj = MyObject()
obj.myiter = myiter

That should do the trick.

Christian
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Re: Doctests and decorated methods don't get along

[Steven D'Aprano]

On Sat, 06 Feb 2010 14:39:00 -0500, Terry Reedy wrote:

> On 2/6/2010 6:48 AM, Steven D'Aprano wrote:
>> It seems that doctest doesn't discover or execute doctests in methods
>> which have been decorated.

[...]

> Doctest has to scan the dict, so it does not see the attribute-lookup
> result.

Ahaha, now we're getting somewhere. If I do this:

>>> import inspect
>>> import test_doctests
>>> method3 = test_doctests.Test.__dict__['method3']
>>> inspect.isfunction(method3)
False
>>> inspect.ismethod(method3)
False

But:

>>> inspect.ismethoddescriptor(method3)
True

which is what I want to see. Presumably doctest.DocTestFinder needs a 
patch to call methoddescriptor's __get__ method.

(BTW, classmethod, staticmethod and property are all special-cased by 
DocTestFinder.)



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Re: How to print all expressions that match a regular expression

[hzh...@gmail.com]

Thanks for your reply.
So there isn't such a routine just because some of the regular
expressions cannot be enumerated. However, some of them can be
enumerated. I guess I have to write a function myself.

Zhuo

On Feb 6, 5:23 pm, Roy Smith  wrote:
> In article
> ,
>
>
>
>
>
>  "hzh...@gmail.com"  wrote:
> > Hi,
>
> > I am a fresh man with python. I know there is regular expressions in
> > Python. What I need is that given a particular regular expression,
> > output all the matches. For example, given ³[1|2|3]{2}² as the regular
> > expression, the program should output all 9 matches, i.e., "11 12 13
> > 21 22 23 31 32 33".
>
> > Is there any well-written routine in Python or third-party program to
> > do this? If there isn't, could somebody make some suggestions on how
> > to write it myself?
>
> > Thanks.
>
> > Zhuo
>
> Please enumerate all the strings which match ".*".  Use additional sheets
> of paper if needed.

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sshd in python for windows 7

[News123]

Hi,

I wondered which modules would be best to perform following task:

A user uses a standard ssh (e.g. putty or openssh) client and performs
an ssh to a windows host

The windows host would run a python script acting as ssh server.

Instead of controlling a shell the user would directly have access to
stdin/stdout/stderr of another python script.


Another option would of course be to install a non python sshd for windows.

The only ssh server for windows, that I know is however a little heavy
as it is openssh under cygwin (and I only used it on XP hosts.)

I'm still not sure, whether python as sshd is a good choice or whether
any other sshd would be better.

bye


N












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Re: how to make a SimpleXMLRPCServer abort at CTRL-C under windows

[News123]

Hi Gabriel,

Gabriel Genellina wrote:
> En Fri, 05 Feb 2010 20:03:51 -0300, News123  escribió:
> 
>> I'm using an XMLRPC server under Windows.
>>
>> What I wonder is how I could create a server, that can be killed with
>> CTRL-C
>>
>> The server aborts easily with CTRL-BREAK but not with CTRL-C (under
>> Windows)
>>
>> If I press CTRL-C it will only abort when the next RPC call occurs.
>> It seems it is blocking in the select() call in the handle_request()
>> function.
> 
> Python 2.6 and up behaves exactly as you want.
> On previous versions you may use this:
> 
> class MyXMLRPCServer(SimpleXMLRPCServer.SimpleXMLRPCServer):
> 
> ... your methods ...
> 
> if not hasattr(SimpleXMLRPCServer.SimpleXMLRPCServer, 'shutdown'):
> 
> # pre 2.6
> quit = False
> 
> def serve_forever(self):
> while not self.quit:
> self.handle_request()
> 
> def shutdown(self):
> self.quit = True
> 
> def server_bind(self):
> self.socket.settimeout(1.0)
> SimpleXMLRPCServer.SimpleXMLRPCServer.server_bind(self)
> 

Overloading  server_bind() with your version solved my problem.

thanks again

N
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Re: How to print all expressions that match a regular expression

[Steven D'Aprano]

On Sat, 06 Feb 2010 16:05:15 -0800, hzh...@gmail.com wrote:

> Thanks for your reply.
> So there isn't such a routine just because some of the regular
> expressions cannot be enumerated. However, some of them can be
> enumerated. I guess I have to write a function myself.

How do you expect to tell the ones that can be enumerated apart from 
those that can't be?

Regular expressions are programs in a "regex" programming language. What 
you are asking for is the same as saying:

"Is there a program that can enumerate every possible set of data that is 
usable as valid input for a given program?"

This, in turn, is equivalent to the Halting Problem -- if you can solve 
one, you can solve the other. You might like to google on the Halting 
Problem before you spend too much time on this.

(Note, however, it isn't necessary to solve the Halting Problem for *all* 
cases in order to have a useful Endless Loop Detector program.)

Why do you think you need this? Seems to me you're starting on an 
extraordinarily difficult job. I hope the benefit is equally 
extraordinary.


[Aside: Python regexes aren't Turing Complete. I'm not sure about Perl 
regexes. Either way, this might actually be less difficult than the 
Halting Problem, as in "amazingly difficult" rather than "impossible".]


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Re: xmlrcp - how to marshall objects

[Jean-Michel Pichavant]

Adam Tauno Williams wrote:

On Fri, 2010-02-05 at 18:24 +0100, Jean-Michel Pichavant wrote:
  

Jean-Michel Pichavant wrote:

Deos anyone knows where to find an code sample describing how to 
implement the interface to marshall one object into XMLRPC compliant 
structures ?
I googled without any success, and what google does not find does not 
exist.

Let say I have this very simple class:
class Point:
   def __init__(self, x, y):
   self.x = x
   self.y = y
I've looked into xmlrpc code, I see  2 options:
1/ override the Marshaller class of client and server
2/ looks like the lib is supporting a WRAPPER list system, it uses to 
Marshall Datetime & Binary object. Can it be possible to add its own 
class (could require to emplement the 'encode' method)
I sense I will spend much more time than required unless someone is 
pointing me in the right direction.
  
I realized I gave a poor example, actually the Point object is marshable 
(marshallable ? like to invent new words), xmlrpc will try to marshall 
using __dict__ if possible.

import os
class Point:
   def __init__(self, x, y):
   self.x = x
   self.y = y
   self.notMarshallable = os



This example doesn't make any sense.  Why would you set a variable equal
to an important module in a class named Point?

What is it you are actually trying to accomplish?  If you are trying to
create an object publishing environment then maybe something like -

rpc = xmlrpclib.loads(payload, use_datetime=True)
method = rpc[1].split('.')
classname   = method[0]
methodname = method[1]
parameters  = rpc[0]
classclass = eval(classname)
handler = classclass()
call = getattr(handler, method_name)
result = apply(call, parameters)
result = xmlrpclib.dumps(tuple([result]), methodresponse=True)

Obviously add copious amounts of exception handling and a security
model.
  


I just took the first non marshallable object that came to my mind. So 
yes that makes no sense but it was an example.


I'll try to sitck to what I'm really trying to do.

I have 2 classes, defined on server side

class Pool:
   def foo():
  return 42

class Stream:
   def __init__(self, pool):
  """@param pool: the pool the stream belongs so."""
  self._pool = pool


I won't need any more detail I think for my example.

Now If I want to return a stream, sending it to the client, I can't 
because xmlrpclib won't be able to marshall _pool.

What I need is the sever being able to marshall a Stream.

I would like to overide the marshall method of that stream, so that 
instead of raising an error because self._pool is not marshallable, it 
sends an int instead identifying the pool on the server side.


class Pool:
   instances = {}

when marshalling a stream:
   id = some_unique_generated_int()
   Pool.instances[id] = self._pool
   self._pool = id # an int will be gracefully marshalled by the defaut 
marshaller

   # call here the default marshaller

Then, when unmarshalling, the server can reassign the _pool reference 
using the id provided by the client.


I hope I am being clear.

JM
  


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Re: Doctests and decorated methods don't get along

[Steven D'Aprano]

On Sat, 06 Feb 2010 14:39:00 -0500, Terry Reedy wrote:

> On 2/6/2010 6:48 AM, Steven D'Aprano wrote:
>> It seems that doctest doesn't discover or execute doctests in methods
>> which have been decorated [by method descriptors].

[...]

>> This looks like  bug to me. Have I missed anything?
> 
> I would call it a limitation as I do not see the doc as promising
> otherwise. I believe doctest predates the descripter protocol, at least
> in its current form, so it may not be completely descriptor-aware. You
> certainly could file a feature request for improved recognition and
> subsequent calling of __get__. An initial patch would improve chances of
> action.

I have found an existing report for this issue:

http://bugs.python.org/issue4037

The original poster's suggested fix was on the right track, but not 
complete. I've added a patch which works according to my tests.

Since this report is currently unassigned, is there a protocol for 
raising its profile and having somebody check my patch for inclusion? 
Should I just send an email to python-dev?


-- 
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Re: How to print all expressions that match a regular expression

[Alf P. Steinbach]

* Steven D'Aprano:

On Sat, 06 Feb 2010 16:05:15 -0800, hzh...@gmail.com wrote:


Thanks for your reply.
So there isn't such a routine just because some of the regular
expressions cannot be enumerated. However, some of them can be
enumerated. I guess I have to write a function myself.


How do you expect to tell the ones that can be enumerated apart from 
those that can't be?


Regular expressions are programs in a "regex" programming language. What 
you are asking for is the same as saying:


"Is there a program that can enumerate every possible set of data that is 
usable as valid input for a given program?"


This, in turn, is equivalent to the Halting Problem -- if you can solve 
one, you can solve the other. You might like to google on the Halting 
Problem before you spend too much time on this.


Hm, well, text editors /regularly/ do repeated regular expression searches, 
producing match after match after match, on request.


To use that /expression/, it seems that Theory is yet again up against Hard 
Reality.

In such a contest where something doesn't quite /match/, is the Map, the 
Terrain, or perhaps the Interpretation of how the Map applies to Terrain, at fault?



(Note, however, it isn't necessary to solve the Halting Problem for *all* 
cases in order to have a useful Endless Loop Detector program.)


Why do you think you need this? Seems to me you're starting on an 
extraordinarily difficult job. I hope the benefit is equally 
extraordinary.


Depending on the application there may be more efficient ways than applying a 
general purpose regexp matcher.


Don't know about modern *nix but in the old days there were different greps for 
different purposes, egrep, fgrep, whatever.


Aside: the only article by Niklaus Wirth that I can remember reading was about 
how to transform algorithms to more efficient ones by exploiting the invariants, 
and one of his examples was simple text searching, where you can advance the 
pattern a number of characters depending on the current non-matching character.



[Aside: Python regexes aren't Turing Complete. I'm not sure about Perl 
regexes. Either way, this might actually be less difficult than the 
Halting Problem, as in "amazingly difficult" rather than "impossible".]



Cheers,

- Alf
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max / min / smallest float value on Python 2.5

[duncan smith]

Hello,
  I'm trying to find a clean and reliable way of uncovering 
information about 'extremal' values for floats on versions of Python 
earlier than 2.6 (just 2.5 actually).  I don't want to add a dependence 
on 3rd party modules just for this purpose.  e.g. For the smallest 
positive float I'm using,



import platform
if platform.architecture()[0].startswith('64'):
TINY = 2.2250738585072014e-308
else:
TINY = 1.1754943508222875e-38


where I've extracted the values for TINY from numpy in IDLE,


>>> float(numpy.finfo(numpy.float32).tiny)
1.1754943508222875e-38
>>> float(numpy.finfo(numpy.float64).tiny)
2.2250738585072014e-308
>>>


I'm not 100% sure how reliable this will be across platforms.  Any ideas 
about the cleanest, reliable way of uncovering this type of information? 
 (I can always invoke numpy, or use Python 2.6, on my home machine and 
hardcode the retrieved values, but I need the code to run on 2.5 without 
3rd part dependencies.)  Cheers.


Duncan
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Re: Your beloved python features

[Steve Holden]

Bruno Desthuilliers wrote:
> apeach a écrit :
>> I love intuitive type recognition.
>>
>> no need to 'DIM everything AS Integer' etc.!
>>
> 
> not to mention the ever hilarious (that is, when you don't have to
> maintain it) typical Java idiom:
> 
>EveryThing theEveryThing = new EveryThing();
> 
http://www.artima.com/weblogs/viewpost.jsp?thread=42242

regards
 Steve
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Re: xmlrpc slow in windows 7 if hostnames are used

[Jean-Michel Pichavant]

News123 wrote:

Hi JM,

Jean-Michel Pichavant wrote:
  

import socket

# server
server = SimpleXMLRPCServer((socket.gethostname(), 5000),
logRequests=False, allow_none=True)


# client
xmlrpclib.ServerProxy("http://%s.yourdomain.com:%s"; %
(socket.gethostname(), 5000))




Well This was exactly my question.
for virtual web servers I cannot just use the IP-address.
some XMLRPC servers do need the histname within the HTTP-POST request.

  

a valid IP address would make it

if I just replaced the hostname with the IP addres, then certain servers
would not be accessable.

I had to use the IP-address for connecteing

why not using the host names?

, but to pass the hostname in
the HTTP-POST request.

I wondered how to convince puthon's SimpleXMLRPCServer (or any other
standard python xmlrpc server), such, that I can obtain above mentioned
goal.


bye

N
  

I'm puzzled.
Unless my english is failing me, everything would be solved using 
hostnames if I follow you. Why don't you do that ?
I am no network/IP guru, but it sounds very weird to have requests 
rejected when using IP addresses. Are you sure your host names are 
resolved with the same IPM address you are using ?



JM
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Re: max / min / smallest float value on Python 2.5

[Shashwat Anand]

On Sun, Feb 7, 2010 at 6:22 AM, duncan smith
wrote:

> Hello,
>  I'm trying to find a clean and reliable way of uncovering information
> about 'extremal' values for floats on versions of Python earlier than 2.6
> (just 2.5 actually).  I don't want to add a dependence on 3rd party modules
> just for this purpose.  e.g. For the smallest positive float I'm using,
>
>
> import platform
> if platform.architecture()[0].startswith('64'):
>TINY = 2.2250738585072014e-308
> else:
>TINY = 1.1754943508222875e-38
>

The above code is executed on OSX (snow leopard - 64 bit) without any
issue.  Your implementation seems fine to me.

>
>
> where I've extracted the values for TINY from numpy in IDLE,
>
>
> >>> float(numpy.finfo(numpy.float32).tiny)
> 1.1754943508222875e-38
> >>> float(numpy.finfo(numpy.float64).tiny)
> 2.2250738585072014e-308
> >>>
>
>
> I'm not 100% sure how reliable this will be across platforms.  Any ideas
> about the cleanest, reliable way of uncovering this type of information?  (I
> can always invoke numpy, or use Python 2.6, on my home machine and hardcode
> the retrieved values, but I need the code to run on 2.5 without 3rd part
> dependencies.)  Cheers.
>
> Duncan
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>
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Re: max / min / smallest float value on Python 2.5

[Benjamin Kaplan]

On Sat, Feb 6, 2010 at 7:52 PM, duncan smith
 wrote:
> Hello,
>      I'm trying to find a clean and reliable way of uncovering information
> about 'extremal' values for floats on versions of Python earlier than 2.6
> (just 2.5 actually).  I don't want to add a dependence on 3rd party modules
> just for this purpose.  e.g. For the smallest positive float I'm using,
>
>
> import platform
> if platform.architecture()[0].startswith('64'):
>    TINY = 2.2250738585072014e-308
> else:
>    TINY = 1.1754943508222875e-38
>
>
> where I've extracted the values for TINY from numpy in IDLE,
>
>
 float(numpy.finfo(numpy.float32).tiny)
> 1.1754943508222875e-38
 float(numpy.finfo(numpy.float64).tiny)
> 2.2250738585072014e-308

>
>
> I'm not 100% sure how reliable this will be across platforms.  Any ideas
> about the cleanest, reliable way of uncovering this type of information?  (I
> can always invoke numpy, or use Python 2.6, on my home machine and hardcode
> the retrieved values, but I need the code to run on 2.5 without 3rd part
> dependencies.)  Cheers.
>
> Duncan

>>> import platform
>>> platform.architecture()
('32bit', '')
>>> tiny = 2.22e-308
>>> tiny
2.2201e-308

float32 vs. float64 has nothing to do with a 32-bit vs. a 64-bit
platform. It's single precision floating-point (C float) vs.
double-precision floating point (C double). It's used in numpy because
numpy optimizes everything like crazy. Python always uses doubles.
>>> import numpy
>>> numpy.double




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Re: Your beloved python features

[Paul Rubin]

Steve Holden  writes:
>>EveryThing theEveryThing = new EveryThing();
> http://www.artima.com/weblogs/viewpost.jsp?thread=42242

Pretty cool!  I see your blog post criticizing Java's lack of type
inference, and then immediately adjacent to the post there's a banner ad
for a book called "Programming in Scala".  I think I am getting a mixed
message ;-)
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Re: How to print all expressions that match a regular expression

[Steven D'Aprano]

On Sun, 07 Feb 2010 01:51:19 +0100, Alf P. Steinbach wrote:

>> Regular expressions are programs in a "regex" programming language.
>> What you are asking for is the same as saying:
>> 
>> "Is there a program that can enumerate every possible set of data that
>> is usable as valid input for a given program?"
>> 
>> This, in turn, is equivalent to the Halting Problem -- if you can solve
>> one, you can solve the other. You might like to google on the Halting
>> Problem before you spend too much time on this.
> 
> Hm, well, text editors /regularly/ do repeated regular expression
> searches, producing match after match after match, on request.

I think you have completely misunderstood what I'm saying.

I'm not saying that you can't *run* a regular expression against text and 
generate output. That truly would be a stupid thing to say, because I 
clearly can do this:

>>> import re
>>> mo = re.search("p.rr.t", 
... "Some text containing parrots as well as other things")
>>> mo.group()
'parrot'

As you point out, it's not hard to embed a regex interpreter inside a 
text editor or other application, or to call an external library.

What is difficult, and potentially impossible, is to take an arbitrary 
regular expression such as "p.rr.t" (the program in the regex language) 
and generate every possible data ("parrot", "pbrrat", ...) that would 
give a match when applied to that regular expression.

Now, in this case, my example is very simple, and it would be easy to 
enumerate every possible data: there's only 65025 of them, limiting to 
the extended ASCII range excluding NUL (1-255). But for an arbitrary 
regex, it won't be that easy. Often it will be unbounded: the example of 
enumerating every string that matches .* has already been given.

The second problem is, generating the data which gives the output you 
want is potentially very, very, difficult, potentially as difficult as 
finding collisions in cryptographic hash functions:

"Given the function hashlib.sha256, enumerate all the possible inputs 
that give the hexadecimal result 
0a2591aaf3340ad92faecbc5908e74d04b51ee5d2deee78f089f1607570e2e91."

This too is unbounded, but you'll have your work cut out just to find 
*one* match, let alone an infinite number of them.

(In this specific example, your best bet is to try a crib: knowing what 
newsgroup this is, and knowing what I've written in the past, the message 
is predictable for being totally unexpected. And yes, that's a hint. A 
shiny penny for the first person to guess what it is.)

I'm suggesting that, in general, there's no way to tell in advance which 
regexes will be easy and which will be hard, and even when they are easy, 
the enumeration will often be infinite. 


-- 
Steven
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Re: Dreaming of new generation IDE

[bartc]

"Arnaud Delobelle"  wrote in message 
news:m28wb6ypfs@googlemail.com...

"Gabriel Genellina"  writes:


En Fri, 05 Feb 2010 19:22:39 -0300, bartc  escribió:

"Steve Holden"  wrote in message
news:mailman.1998.1265399766.28905.python-l...@python.org...

Arnaud Delobelle wrote:

Robert Kern  writes:


I prefer Guido's formulation (which, naturally, I can't find a direct
quote for right now): if you expect that a boolean argument is only
going to take *literal* True or False, then it should be split into

 ^^^

two functions.


So rather than three boolean arguments, would you have eight 
functions?



If there's genuinely a need for that functionality, yes.


So you want a function such as drawtext(s, bold=true, italic=false,
underline=true) to be split into:

drawtext(s)
drawtextb(s)
drawtexti(s)
drawtextu(s)
drawtextbi(s)
drawtextbu(s)
drawtextiu(s)
drawtextbiu(s)


Note the *literal* part. If you (the programmer) is likely to know the
parameter value when writing the code, then the function is actually two
separate functions.


Thanks, I understand what Steve Holden meant now.


I've just noticed that 'literal' part. But I think I still disagree.

For a real-world example, it means instead of having a room with a 
light-switch in it, if I *know* I want the light on or off, I should have 
two rooms: one with the light permanently on, and one with it permanently 
off, and just walk into the right one.


--
Bartc


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Re: Calendar GUI

[Jean-Michel Pichavant]

Michael Torrie wrote:

Gabriel wrote:
  

On Fri, Feb 5, 2010 at 9:08 PM, William Gaggioli  wrote:


I'm working on setting up some software for a Peruvian non-profit to help
them organize their incoming volunteers. One of the features I'd like to add
is a calendar-like view of the different volunteers arrival dates and
staying time, with potentially some other info through some double-click
action. Rather than writing a calendar gui myself, is there some open-source
calendar program you guys could recommend that I could plug into? It has to
be run locally, as the internet isn't so reliable down here, but other than
that something simple and clean is ideal.
  

I wrote a gtk gui for google calendar.

Maybe you can adapt it to your needs.

http://code.google.com/p/googlecalendar-gtk/



Would this work without an internet connection?  The original poster
stated that internet isn't so reliable, hence the need for a local solution.

  

How about zimbra ?
http://www.zimbra.com/products/calendar-collaboration.html

Ok, that's heavy stuff, but it's free, open source and widely used.

JM

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Re: How to print all expressions that match a regular expression

[MRAB]

Alf P. Steinbach wrote:

* Steven D'Aprano:

On Sat, 06 Feb 2010 16:05:15 -0800, hzh...@gmail.com wrote:


Thanks for your reply.
So there isn't such a routine just because some of the regular
expressions cannot be enumerated. However, some of them can be
enumerated. I guess I have to write a function myself.


How do you expect to tell the ones that can be enumerated apart from 
those that can't be?


Regular expressions are programs in a "regex" programming language. 
What you are asking for is the same as saying:


"Is there a program that can enumerate every possible set of data that 
is usable as valid input for a given program?"


This, in turn, is equivalent to the Halting Problem -- if you can 
solve one, you can solve the other. You might like to google on the 
Halting Problem before you spend too much time on this.


Hm, well, text editors /regularly/ do repeated regular expression 
searches, producing match after match after match, on request.



[snip]
I'm not sure you understood what the OP was requesting: a way of
generating the strings which would match a given regex.
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Re: max / min / smallest float value on Python 2.5

[Christian Heimes]

duncan smith wrote:
> Hello,
>I'm trying to find a clean and reliable way of uncovering 
> information about 'extremal' values for floats on versions of Python 
> earlier than 2.6 (just 2.5 actually).  I don't want to add a dependence 
> on 3rd party modules just for this purpose.  e.g. For the smallest 
> positive float I'm using,
> 
> 
> import platform
> if platform.architecture()[0].startswith('64'):
>  TINY = 2.2250738585072014e-308
> else:
>  TINY = 1.1754943508222875e-38
> 
> 
> where I've extracted the values for TINY from numpy in IDLE,
> 
> 
>  >>> float(numpy.finfo(numpy.float32).tiny)
> 1.1754943508222875e-38
>  >>> float(numpy.finfo(numpy.float64).tiny)
> 2.2250738585072014e-308

You are confusing a 32 / 64bit build with 32 / 64bit floats. Python's
float type is build upon C's double precision float type on both 32 and
64 bit builds. The simple precision 32bit float type isn't used. The
DBL_MIN and DBL_MAX values are equal on all platforms that have full
IEEE 754 float point support. The radix may be different, though.

Christian
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Re: Dreaming of new generation IDE

[Steven D'Aprano]

On Sun, 07 Feb 2010 01:34:14 +, bartc wrote:

> For a real-world example, it means instead of having a room with a
> light-switch in it, if I *know* I want the light on or off, I should
> have two rooms: one with the light permanently on, and one with it
> permanently off, and just walk into the right one.

I don't think you can apply real-world analogies to software in that way. 
They're too different.

Think of the objections to having two rooms, one permanently lit up, the 
other permanently not:

(1) Having two rooms is expensive and wasteful of physical space, which 
is in short supply.

(2) You typically use rooms for storing things (furniture and smaller 
objects), having two rooms mean you would need to clone every object 
inside it and somehow keep them in perfect synchronisation.

(3) the light that is always on will use electricity 24 hours a day, 
regardless of whether you are inside it or not.

But none of those objections apply to functions:

(1) Functions are cheap and live in memory, which is not in short supply 
unless you're programming for an embedded device.

(1a) Even if you are programming in a device that is short of memory, the 
overhead of a second function is minimal. There's little difference 
between:

def func(flag):
if flag:
blockA
else:
blockB


and


def funcA():
blockA

def funcB():
blockB


for any non-trivial code blocks, particularly if any common code is 
factored out into another function which you call.

(2) Functions aren't typically used for storage, and when they need 
external data, it is easy to have them access a common data store.

(3) Functions don't use CPU cycles just by existing.



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Steven
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Re: max / min / smallest float value on Python 2.5

[Steven D'Aprano]

On Sun, 07 Feb 2010 00:52:48 +, duncan smith wrote:

> Hello,
>I'm trying to find a clean and reliable way of uncovering
> information about 'extremal' values for floats on versions of Python
> earlier than 2.6 (just 2.5 actually).  I don't want to add a dependence
> on 3rd party modules just for this purpose.  e.g. For the smallest
> positive float I'm using,

Assuming that your architecture is based on binary floats:

>>> x = 1.0/2
>>> while 0.0 + x != 0.0:
... smallest = x
... x /= 2.0
...
>>> smallest
4.9406564584124654e-324

which is the smallest number that can be distinguished from zero on my 
system.

If you're running on some weird platform with non-binary floats (perhaps 
a Russian ternary mainframe, or an old supercomputer with decimal floats) 
then you're on your own.

I calculated this using Python 2.5. In 2.6, I see this:

>>> sys.float_info
sys.floatinfo(max=1.7976931348623157e+308, max_exp=1024, max_10_exp=308, 
min=2.2250738585072014e-308, min_exp=-1021, min_10_exp=-307, dig=15, 
mant_dig=53, epsilon=2.2204460492503131e-16, radix=2, rounds=1)

So there's obviously a difference between how I calculate the smallest 
number and what Python thinks. The reason for this is left as an exercise.



-- 
Steven
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Re: How to print all expressions that match a regular expression

[Grant Edwards]

On 2010-02-06, Roy Smith  wrote:

>> I am a fresh man with python. I know there is regular expressions in
>> Python. What I need is that given a particular regular expression,
>> output all the matches.
[..]

> Please enumerate all the strings which match ".*".  Use additional sheets 
> of paper if needed.

And be sure to show your work.

-- 
Grant

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