🌐 Mailman 3 July 2009 - Python-list - python.org

Re: Proposal: [... for ... while cond(x)]
by Eighty Sept. 26, 2013

Sept. 26, 2013

Terry Reedy wrote: > whereas the analogous expansion of your proposal > > for x in xs: > while cond(x): > yield e(x) > > is an infinite loop and not at all what you mean. You're right. The syntax is ambiguous. I agree it's not a good idea, now. :) > x for x in xs while cond(x) if blah(x) > x for x in xs if blah(x) while cond(x) > x*y for x in xs while cond(x) for y in ys These wouldn't be a problem. "... for x in xs while cond(x) ..." would be transformed into "... for x in takewhile(cond, xs) ..." which could be applied to an if thingy if you first transform "... for x in xs if cond(x) ..." into "... for x in filter(cond, xs) ...".

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mutlifile inheritance problem
by maurelius01＠hotmail.com Sept. 21, 2013

Sept. 21, 2013

I have classes defined in different files and would like to inherit from a class in file A.py for a class in file B.py but am running into problems. I'm using Python 1.5.2 on Windows NT Here's a specific example: ************************ file cbase01.py: class CBase: def __init__(self): self.cclass = None print "cbase" class CImStream(CBase): def __init(self): CBase.__init__(self) print "CImStream" ************************* in file wrappers_A01.py: import cbase01 reload(cbase01) class ImStream_SavedBitmaps(cbase01.CImStream): def __init__(self): cbase.CImStream.__init__(self) print "SavedBitmaps" ************************** in file sequencer01.py import cbase01 # the offending lines, program works reload(cbase01) # if I comment these out. class Sequencer: def Append(self, item): pass ***************************** in test02.py import wrappers_A01 reload(wrappers_A01) import sequencer01 reload(sequencer01) x0 = wrappers_A01.ImStream_SavedBitmaps() *************************************************************** If I run test02 I get the traceback Traceback (innermost last): File "<string>", line 1, in ? File "D:\PythonCode\pna\eyeTracking\tests\test02.py", line 15, in ? x0 = wrappers_A01.ImStream_SavedBitmaps() File "D:\PythonCode\pna\eyeTracking\tests\wrappers_A01.py", line 21, in __init__ cbase.CImStream.__init__(self) TypeError: unbound method must be called with class instance 1st argument Any ideas what I am doing wrong? Thanks, Marc

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can't find win32api from embedded pyrun call
by Jim Sept. 6, 2013

Sept. 6, 2013

I am trying to figure out how to embed Python in a little C++ Windows console app. Here's the code: // Py_Initialize(); Py_InitializeEx(0); PyRun_SimpleString("from win32com.client import *"); Here's what it does on the last line: File "D:\Python\Lib\site-packages\win32com\__init__.py", line 5, in ? import win32api, sys, ok ImportError: No module named win32api The same line runs fine in IDLE or at the command prompt. It also runs without complaint if I run a release version of the app. To build the debug version I had to build python42_d.lib/dll myself. The reason I can't call PyInitialize is that it crashes with an "invalid signal" error. I don't think it's a path issue -- I've checked system path, sys.path, pythonpath env var, and the pythonpath entry in the registry, all of them loaded with directories including the one with win32api.pyd. Besides, if it were an install or path problem, why would it work at the command prompt? Could it be a problem with the debug lib I built? Any suggestions are welcome. -- Jim

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Best Python book(s) for a pre-teen?
by snarflemike＠yahoo.com Aug. 1, 2013

Aug. 1, 2013

Hi all, My son is 11 and wants to try programming, partly because it's what I do for a living. Even though I don't (yet?) use or even know Python, through some unexplainable thought process I've decided it would be a good language to start him off with. I've downloaded 2.2.2 and played around with it for a bit, and I would now like to hand him a book (with my guidance as needed) and say "go have fun!" Is there a book that would be suitable for this approach (again, assuming I'm around to help out as needed)? One other question -- I'd like him to be able to do simple graphics fairly early, since I think it makes the whole self-learning process much more interesting. I'm talking about things like points, lines, circles, fills, etc. Is there a binding to the Win32 graphics primatives in 2.2.2, or can I find one someplace? If this is a RTFM question, any pointers to TFM chapter, etc would be appreciated! Thanks for any guidance. I'm sure I'll end up having at least as much fun as he does. Mike

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Q: "Best" book for teaching
by grkuntzmd＠gmail.com July 27, 2013

July 27, 2013

I am considering teaching an "introduction to programming" course for continuing education adults at a local community college. These would people with no programming experience, but I will require a reasonable facility with computers. What would be a good book to use as the text for the course? Thanks.

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Tutorials on Jinja
by Saurabh July 15, 2013

July 15, 2013

Hi All, I am trying to move my application on a MVC architecture and plan to use Jinja for the same. Can anyone provide me with few quick links that might help me to get started with Jinja? Thanks, Saby

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Re: python for loop
by Steven D'Aprano July 10, 2013

July 10, 2013

On Wed, 01 Apr 2009 04:39:26 +0100, Rhodri James wrote: > Dragging this back to the original topic, you clearly find starting list > indices from zero unintuitive. To me, with a mathematical background, > it's not just intuitive, it's correct. All sorts of useful properties > fall out from that, not the least of which is the fact that > "a[0:len(a)]" slices the whole of a list. But some non-useful properties fall out of that too. Want the fifth item? a[5] gives you the *sixth* item, which is weird, so you have to use a[5-1] to get the fifth item. There is a major clash between the names of ordinals in human languages and zero-based counting. In human languages, the Nth-ordinal item comes in position N. You can keep that useful convention with zero-based counting by inventing the ugly word "zeroth", but that just leads to bizarro-talk like "the zeroeth item comes first, the first item comes second, and so on". a[0:len(a)] is legal, a[0] is legal, but surprisingly a[len(a)] is an error. Despite coming from a Pascal background, I've come to appreciate and prefer zero-based indexing for programming. But I'm not blind to the disadvantages. I'll often work out an algorithm using pencil and paper and counting from one, and then subtract one to get zero-based indexes. There are advantages and disadvantages to both systems, but on balance, I think that zero-based is a better system for programming, and one-based for natural language. -- Steven

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Coping with cyclic imports
by Torsten Bronger July 6, 2013

July 6, 2013

Hallöchen! I have a rather fat module that represents a document parser -- inline elements, block elements, and the like. Now I want to split it into many modules to make everything more manageable. But at the moment I don't see how to avoid cyclic imports: A document element A, which is represented my module parser.A, may contain the element B, as defined in parser.B. And vice versa. So both modules must import each other, as far as I can see. I know that cyclic imports work in Python under certain circumstances. Can anyone refer me to a page which explains *when* this works? Because at least once, the imported module was not "finished" and thus largely unusual. Thank you! Tschö, Torsten. -- Torsten Bronger, aquisgrana, europa vetus Jabber ID: bronger(a)jabber.org (See http://ime.webhop.org for further contact info.)

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June 12, 2013

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how to get next month string?
by Yinghe Chen May 2, 2013

May 2, 2013

Hi, Could someone help on how to use python to output the next month string like this? "AUG07", suppose now is July 2007. I think also need to consider Dec 07 case, it is supposed to output as below: "JAN07". datetime module seems not supporting the arithmatic operations, any hints? Thanks in advance, Yinghe Chen

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