🌐 Mailman 3 August 2007 - Python-list - python.org

Re: So what exactly is a complex number?
by iapain Aug. 31, 2007

Aug. 31, 2007

> > On Thu, 2007-08-30 at 20:11 -0500, Lamonte Harris wrote: > > > Like in math where you put letters that represent numbers for place > > > holders to try to find the answer type complex numbers? You shouldnt worry about it in python, its pretty large to handle all your calc.

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Re: status of Programming by Contract (PEP 316)?
by Russ Aug. 31, 2007

Aug. 31, 2007

> I've always wondered... Are the compilers (or interpreters), which take > these programs to machine code, also formally proven correct? No, they are not formally proven correct (too complicated for that), but I believe they are certified to a higher level than your "typical" compiler. I think that Ada compilers used for certain safety-critical applications must meet higher standards than, say, GNU Ada, for example. And the OS > in which those programs operate, are they also formally proven correct? Same as above, if I am not mistaken. > And the hardware, microprocessor, electric supply, etc. are they also > 'proven correct'? I think the microprocessors used for flight control, for example, are certified to a higher level than standard microprocessors. How would you prove a power supply to be "correct"? I'm sure they meet higher reliability standards too.

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Setting a read-only attribute
by tleeuwenburg＠gmail.com Aug. 31, 2007

Aug. 31, 2007

I have an object and wish to set an attribute on it which, unfortunately for me, is read-only. How can I go about this? Cheers. -T

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Complex Numbers
by Greg Lindstrom Aug. 31, 2007

Aug. 31, 2007

> ---------- Forwarded message ---------- > From: "Lamonte Harris" <pyth0nc0d3r(a)gmail.com> > To: python-list(a)python.org > Date: Thu, 30 Aug 2007 20:11:14 -0500 > Subject: So what exactly is a complex number? > Like in math where you put letters that represent numbers for place > holders to try to find the answer type complex numbers? Not quite. Consider the square root of -1. It's not real because you can't square a real number and get a negative, so we define "i" (or, perhaps "j") to be the square root of -1. An imaginary number is of the form Ai, where A is "real". So 2i, -3.14i are imaginary. Complex Numbers are of the form A + Bi Where A and B are real (so they have a "real" component and am "imaginary" component). So yo might see 2 + 3i, etc. You'll see them a lot in engineering.

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win32com problem: more than one instance
by Thomas Rademacher Aug. 31, 2007

Aug. 31, 2007

Hello, I start my script convert.py simultaneously in any dos-shells several times. But I get every time the same solidworks instance. I see in the proccess (task) manager only one solidworks.exe Therefore I get for all simultaneous conversions the same output file. I tested the same code with excel (test_excel.py) and her I get many instances of excel in proccess (task) manager. How can I get many instances of solidworks? Is it a problem of python? Or is it a problem of the Solidworks-COM-Implemention and I get the same problem with an C++ client implementation? Thanks for your help, Thomas convert.py import pythoncom pythoncom.CoInitializeEx(pythoncom.COINIT_MULTITHREADED) sldworks = gencache.EnsureModule('{83A33D31-27C5-11CE- BFD4-00400513BB57}', 0x0, 13, 0) sw = sldworks.ISldWorks(DispatchEx('SldWorks.Application')) swmodel, errors, warnings = sw.OpenDoc6(sourceName, constants.swDocPART, constants.swOpenDocOptions_Silent, "") activeDoc = sw.ActiveDoc retval, errors, warnings = swmodel.SaveAs4(targetName, constants.swSaveAsCurrentVersion , constants.swOpenDocOptions_Silent ) pythoncom.CoUninitialize() test_excel.py import pythoncom pythoncom.CoInitializeEx(pythoncom.COINIT_MULTITHREADED) myExcel = win32com.client.DispatchEx('Excel.Application') myExcel.Visible = 1 Excel = myExcel.Workbooks.Open(excelfile, 0, False, 2) Excel.Saved = 1 Excel.Close() myExcel.Quit() del myExcel del Excel pythoncom.CoUninitialize()

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Fatal Python error using ctypes & python exceptions
by mmacrobert Aug. 31, 2007

Aug. 31, 2007

Hi Everyone, I've created a 'C' dll that is accessed via ctypes library containing a bunch of functions. I've successfully been able to use the functions. However, I would like to throw python exceptions from some of them. I throw them using: ::PyErr_SetString(::PyExc_RuntimeError, theErrorString); I crash the console when this function is invoked in the 'C' domain. I get an error stating: Fatal Python error: PyThreadState_Get: no current thread when the calling code in python is: try: cdll.MyDll.ThrowingFunction() except: print "An error has occurred" The dll is just a plain win32 'C' dll, built with an MS compiler. How do I throw python exceptions correctly? Is there some kind of "init" function that needs to be called? Any help much appreciated. Thanks, Martin

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MySQLdb ImportError
by Sjoerd Aug. 31, 2007

Aug. 31, 2007

Hello! When I try to import the MySQLdb lib python generates an error: Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> import MySQLdb File "C:\Python25\lib\site-packages\MySQLdb\__init__.py", line 19, in <module> import _mysql ImportError: DLL load failed with error code 193 This is on a AMD64 bit machine, when I import it on a 32 bit machine it works fine. Is there anyway to fix this? Is there a build for AMD64 bit machines or is there simply no way that I can get MySQLdb working on it? Thanks in advance, Sjoerd

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Re: fcntl problems
by mhearne808[insert-at-sign-here]gmail[insert-dot-here]com Aug. 31, 2007

Aug. 31, 2007

On Aug 31, 12:23 am, Miles <semantic...(a)gmail.com> wrote: > Sorry, that last quote-only reply was accidental. :) > > On 8/30/07, mhearne808 wrote: > > I've been doing some experiments, and here are some specific examples > > to try. > > [snipped examples] > > > From these last two experiments I can only conclude that file locking > > isn't doing a durned thing. > > > What's going on? > > File locking isn't doing a durned thing in those cases because you're > only obtaining the lock from a single process. > > > According to my Python Cookbook: > > "Exclusive lock: This denies all _other_ processes both read and write > > access to the file." > > This is only for mandatory locking; POSIX flock is advisory locking, > which states: "Only one process may hold an exclusive lock for a given > file at a given time." Advisory locks don't have any effect on > processes that don't use locks. Mandatory locks are kernel enforced, > but non-POSIX and not available in Mac OS X. > > -Miles I think I'm still confused. Maybe I should explain the behavior that I want, and then figure out if it is possible. I have a script that will be run from a cron job once a minute. One of the things this script will do is open a file to stash some temporary results. I expect that this script will always finish its work in less than 15 seconds, but I didn't want to depend on that. Thus I started to look into file locking, which I had hoped I could use in the following fashion: Process A opens file foo Process A locks file foo Process A takes more than a minute to do its work Process B wakes up Process B determines that file foo is locked Process B quits in disgust Process A finishes its work Since I couldn't figure out file locking, I decided to just have Process A create a "pid" file in the directory - analogous to the "Occupied" sign on an airplane bathroom. This works, but it seems a little hacky. --Mike

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Re: list index()
by TheFlyingDutchman Aug. 31, 2007

Aug. 31, 2007

> > Fair enough, but that's a tutorial. It would be foolish to demand that a > tutorial be a complete reference for everything that can be done with a list. I wasn't demanding anything of the page. I was pointing out how I made the assumption there was no way to find out if a list has a value other than by using index(). I am not used to having keywords in a language operate on a data structure, in addition to its methods. > The page lists all methods of list objects, but there are more things one can > do with lists that don't look like method calls. For example, it doesn't say > that you can compare lists. It doesn't say that you can read and write > elements in the lists. Would you automatically assume that those things aren't > possible? I hope not. (Of course, those operations are handled by the magical > methods __eq__, __setitem__, __getitem__ etc, but I think one can forgive the > tutorial for not mentioning those in the interest of not confusing beginners.) > > By your logic, no web page would be allowed to say anything about lists unless > it says *everything* about lists, and that wouldn't be very useful. As I just stated, I wasn't making a criticism of the page. But since you are defending it, let's talk about Python documentation from the perspective of an experienced programmer who is a new/casual user of both Python and Java. If I am in the process of writing a little Java program, java.sun.com provides documentation on its data structures that show up right at the top of a google search for "Java ArrayList", "Java Hashtable", etc. If I am writing a little Python program and want to see what I can do with a list, I google "python list" I get the tutorial page that has been mentioned. Then the next query result is a page that is titled the "Python Language Reference". But in this reference page for "python str,unicode,list,tuple,buffer,xrange", I see operators that work on lists and other data structures that I an mot concerned with, but there is no list of "list methods". But I do see navigational arrows that I hopefully assume will take me to a page where I can find all the list methods - but that is not the case. I go from "3.6 Sequence Types -- str, unicode, list, tuple, buffer, xrange" to "3.6.1 String Methods" to "3.6.2 String Formatting Operations" to "3.6.3 XRange Type" to "3.6.4 Mutable Sequence Types". And then I'm done with 3.6 of the Python Language Reference and I never saw a list of list methods or a page devoted to lists. So I bounce out to the table of contents assuming that there must be an entry for "list" that will show all the list methods and operators and give me a summary ala Java ArrayList. But all I find are entries for UserList and AddressList. :(

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How to use "Resource Editor" in wxPython ?
by codemania Aug. 31, 2007

Aug. 31, 2007

Disappointing me extremely, with the "generate python" function within Resource Editor, I only get a segment of python code which load xrc(xml format) file, rather than real python code in which I could append my own code. Does that mean RE(Resource Editor) is of little use? I hope not, maybe the way I use it is wrong? Tell me please.

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