Sys.path entries

[Gabriel Genellina]

En Thu, 31 Dec 2009 04:31:06 -0300, Marco Salden <marco.salden at gmail.com>  
escribió:

> On Dec 30, 8:13 pm, Alan Harris-Reid <a... at baselinedata.co.uk> wrote:
>> Hi there,
>>
>> In my sys.path (interpreter only, no application loaded), I have the
>> following strange entries...
>> 'C:\\WINDOWS\\system32\\python31.zip'.  This file does not exist
>> anywhere (although python31.dll does exist in \windows\system32\), where
>> could it have come from?
>> 'C:\\program files\\python31\\lib\\plat-win'.  There is no such
>> directory, although I can see that this has been added by the PYTHONPATH
>> varible in PyConfig.h (when is this loaded?)
>>
>> Is there any way of removing these entries, or are they best left where
>> they are?  (I am using Python 3.1 on WinXP)
>>
>
> Same for me: C:\Windows\system32\python25.zip is in the only non-"C:
> \Python25" directroy&file in my sys.path (under Python 2.5).
> No idea why it needs it. And also in my case the zip file isnt in that
> location anyway. So also not 3K only or so.
> But I have no issues with it (so far :-)), do you? Do you run into
> problems because of this in the path?

Don't worry. The pythonNN.zip entry in sys.path is required to allow a  
complete Python install to reside in a .zip file -- all modules used at  
start time (os, ntpath, site...) must be importable before user code has a  
chance of altering the import mechanisms. Tools like py2exe may take  
advantage of that. See PEP 273: http://www.python.org/dev/peps/pep-0273/
Normally, such zip file doesn't exist, and Python just ignores its  
sys.path entry; look at sys.path_importer_cache:

py> sys.path_importer_cache
...
  'C:\\WINDOWS\\system32\\python26.zip': <imp.NullImporter object at  
0x00AB0028>,
  'd:\\apps\\python26\\lib\\plat-win': <imp.NullImporter object at  
0x00AB0480>,
  'd:\\apps\\python26\\lib\\site-packages': None,
...

Same for the plat-win directory; someone *could* use it for  
Windows-specific stuff, but it doesn't exist by default and is simply  
ignored.

>> Also, regarding PyConfig.h - is this read every time I start Python.exe?

No. It's a copy of the .h file used when Python was compiled from its C  
sources. distutils may read it to gather some information. Unless you  
compile the interpreter from source yourself, it serves no other purpose  
than document the options originally used to compile it.

-- 
Gabriel Genellina