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

Re: list index()
by zzbbaadd＠aol.com Aug. 31, 2007

Aug. 31, 2007

On Aug 30, 4:48 pm, "Chris Mellon" <arka...(a)gmail.com> wrote: > On 8/30/07, zzbba...(a)aol.com <zzbba...(a)aol.com> wrote: > > > > > On Aug 30, 4:31 pm, Ben Finney <bignose+hates-s...(a)benfinney.id.au> > > wrote: > > > zzbba...(a)aol.com writes: > > > > In my case of have done os.listdir() on two directories. I want to see > > > > what files are in directory A that are not in directory B. > > > > You get that information unambiguously. It's an exceptional case, > > > since there's no index to return, so it throws an exception. > > > > > I have used exceptions in other languages and only do so on logic > > > > that should never happen. > > > > You're confusing "assert" ("this should always be true") with > > > "exception" ("this is an exception to the the normal flow of this > > > process"). > > > > An exception isn't "something that should never happen", it's > > > something that is entirely possible and needs to be handled somehow. > > > I don't think that is the definition used across computer science. > > how its defined in Python is what is important in this context. Is there a definition on python.org for an exception? > > > It suddenly dawned on me that what would be best would be a contains() > > (or IN syntax for those who can't afford to wait) for lists. > > > if mylist.contains("hello): > > Genius. Why didn't anyone think of that before? With an attitude like that Chris, don't expect to be getting an invite to beta test my Python 3 fork.

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Re: list index()
by zzbbaadd＠aol.com Aug. 31, 2007

Aug. 31, 2007

> Either I'm misunderstanding what you mean or you need to get a clue > about what Python can already do before you go around making suggestions > for what Python needs. Lists have supported "in" tests since at least > version 1.5.2: > Well IN was what I was looking for and would have saved this thread. However I don't believe IN showed up on the doc web page that has list methods, where I found index().

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Re: list index()
by aleax＠mac.com Aug. 31, 2007

Aug. 31, 2007

Ricardo Aráoz <ricaraoz(a)gmail.com> wrote: ... > Alex Martelli wrote: > > <zzbbaadd(a)aol.com> wrote: > > ... > >> In my case of have done os.listdir() on two directories. I want to see > >> what files are in directory A that are not in directory B. > > > > So why would you care about WHERE, in the listdir of B, are to be found > > the files that are in A but not B?! You should call .index only if you > > CARE about the position. > > > > def inAnotB(A, B): > > inA = os.listdir(A) > > inBs = set(os.listdir(B)) > > return [f for f in inA if f not in inBs] > > > > is the "one obvious way to do it" (the set(...) is just a simple and > > powerful optimization -- checking membership in a set is roughly O(1), > > while checking membership in a list of N items is O(N)...). > > And what is the order of passing a list into a set? O(N)+? Roughly O(N), yes (with the usual caveats about hashing costs, &c;-). So, when A has M files and B has N, your total costs are roughly O(M+N) instead of O(M*N) -- a really juicy improvement for large M and N! Alex

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Re: list index()
by Lawrence D'Oliveiro Aug. 31, 2007

Aug. 31, 2007

In message <mailman.158.1188499243.28954.python-list(a)python.org>, Steve Holden wrote: > But why would you want to ignore built-in support like "value in dict"? Because a function can be passed as a value in its own right, a built-in construct cannot.

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

Aug. 31, 2007

Ryan Ginstrom wrote: > I tried using DBC for a time in C++ (using a library with a clever > assembly-language hack). I personally found it neater having such code in > unit tests, but obviously, it's a matter of preference. I agree that it ultimately boils down to preference, but as I tried to explain earlier, I don't think that unit tests are equivalent to DBC (or, as I referred to it earlier, "self-testing code"). Unit tests are not automatically executed when you run your application. You need to write the drivers and generate sample inputs to all the functions in your application, which can be very time-consuming. And if you think you can anticipate all the weird internal data that might come up in the execution of your application, then either your application is very simple or you are fooling yourself. With self-testing code, on the other hand, all you need to do is to get sample inputs to your application (not internal inputs to functions) and run the entire application. That is much simpler and more comprehensive than unit testing. Again, I recognize that it doesn't necessarily replace unit testing completely. For one thing, unit testing can test for specific outputs for specific inputs, whereas you wouldn't want to clutter your actual code with such specific cases. For example, a unit test for a sorting function could provide a specific input and test for a specific output, but you probably wouldn't want to clutter your code with such a case. The self-tests in your code would be more for general tests. PEP 316 provides an excellent of comprehensive tests for a sorting function. If you pass those tests, you can be sure your function worked correctly.

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wx.DirDialog defaultPath
by Woo, Daniel Aug. 31, 2007

Aug. 31, 2007

Is there some kind of parsing/checking that is done on the defaultPath? The path I would like to set as default is something like this: "c:\Somedirectory\engineering\somedirectory". When providing this as the default, the control seems to think it is an invalid path, although it IS a valid path under Windows. I'm pretty sure this is because two directories in the hierarchy have the same name. Since it believes this is an invalid path, the dialog opens up browsing in the root directory. I can successfully set the default to other directories, nested as deep as I want and it works as expected. Anyway around this? Thanks!

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python + gcov
by labrach＠gmail.com Aug. 30, 2007

Aug. 30, 2007

Hi I want to profile (and analyse coverage) some c++ code imported as a python module I've compiled python (2.4.2) with gcc 3.4.3 and flags=-Wall -fprofile- arcs -ftest-coverage in order to use gcov. However, the python binary does not generate any coverage file (such than *.gcno, gcda) during execution. any tips ? or may be another method to profile c++ wrapped modules within python ? thanks laurent

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Re: status of Programming by Contract (PEP 316)?
by Russ Aug. 30, 2007

Aug. 30, 2007

> Things get vetted *before* they get added to the core, not after. I realize that. I meant that it would get vetted in the process of putting it into the core. That would provide more confidence that it was done the best possible way -- or close to it.

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Unzip: Memory Error
by mcl Aug. 30, 2007

Aug. 30, 2007

I am trying to unzip an 18mb zip containing just a single 200mb file and I get a Memory Error. When I run the code on a smaller file 1mb zip, 11mb file, it works fine. I am running on a hosted Apache web server I am using some code I found on the web somewhere. def unzip_file_into_dir(file, dir): #os.mkdir(dir, 0777) zfobj = zipfile.ZipFile(file) for name in zfobj.namelist(): if name.endswith('/'): os.mkdir(os.path.join(dir, name)) else: outfile = open(os.path.join(dir, name), 'wb') outfile.write(zfobj.read(name)) outfile.close() Error Traceback: Line 357 gives the Memory Error I have removed paths from file references ============================================== MemoryError Python 2.3.4: /usr/bin/python Wed Aug 29 19:38:22 2007 A problem occurred in a Python script. Here is the sequence of function calls leading up to the error, in the order they occurred. /qlunzip.py 58 59 60 if __name__ == "__main__" : 61 unzipMain() 62 unzipMain = <function unzipMain> /qlunzip.py in unzipMain() 53 destdir = getDestDir() 54 print destdir, gv.nl 55 unzip_file_into_dir(zips, destdir) 56 57 global unzip_file_into_dir = <function unzip_file_into_dir>, zips = '/ pcodes.zip', destdir = '/pcodes/' /qlunzip.py in unzip_file_into_dir(file='pcodes.zip', dir='pcodes/') 34 else: 35 outfile = open(os.path.join(dir, name), 'wb') 36 outfile.write(zfobj.read(name)) 37 outfile.close() 38 outfile = <open file 'pcodes/pcodes.lst', mode 'wb'>, outfile.write = <built-in method write of file object>, zfobj = <zipfile.ZipFile instance>, zfobj.read = <bound method ZipFile.read of <zipfile.ZipFile instance>>, name = 'pcodes.lst' /usr/lib/python2.3/zipfile.py in read(self=<zipfile.ZipFile instance>, name='pcodes.lst') 355 # zlib compress/decompress code by Jeremy Hylton of CNRI 356 dc = zlib.decompressobj(-15) 357 bytes = dc.decompress(bytes) 358 # need to feed in unused pad byte so that zlib won't choke 359 ex = dc.decompress('Z') + dc.flush() bytes = '\xc4\x9d]\x93\xab8\x92\x86\xef7b\xff\x83\xa3/\xf6f\xba \xa7\xe7\xa2g#vwf6\x8a\x02\xc3\xd04\x8d\r\x1e\x7f\xdclP\xb6\xcav\x1c \xca\xd4`\xfbx...; \xb7jp\x06V{\xaf\xc3\xa5\xa7;\xdd\xd2\xaaD\x7f)c \xc6\x9d\x0f\xf2\xff-\xc9\x92\xc3\x1d\xa4`\xe0\xb8\x06)\x188\x9cA\n \x06\x8e\x1bPc\xf8\xf0\x1f', dc = <zlib.Decompress object>, dc.decompress = <built-in method decompress of zlib.Decompress object> MemoryError: args = () ============================================================ Any help much appreciated Richard

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Re: Please assist- Python Consultant needed for 3-6 month project
by Alan Meyer Aug. 30, 2007

Aug. 30, 2007

On Aug 30, 12:06 pm, "Kelley McNeillie" <kmcneil...(a)softwarespecialists.com> wrote: > ... We are looking for a python developer with web-based > application experience. ... I am finding this skill pretty much > impossible to identify locally ... Kelley, I don't know if your client is willing to pay for a week or two of non-productive time, but I think a good Perl programmer with web development experience could pick up Python in a week, and a good Java or C# programmer could pick it up in two weeks. I've personally always believed that, when comparing a good programmer with no specific experience in a particular language, and an average programmer with lots of experience, the good programmer will outperform the average one in any task lasting more than a couple of months. Of course I haven't always been able to convince managers of that. Alan

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