[python-win32] HKLM\Software\Python\PythonCore\2.6\PythonPath - does it serve any purpose?

[Paul Keating]

What is the registry key HKLM\Software\Python\PythonCore\2.6\PythonPath for? The docs (http://www.python.org/doc/2.6/using/windows.html) say

  Modifying the module search path can also be done through the Windows registry: Edit HKEY_LOCAL_MACHINE\SOFTWARE\Python\PythonCore\version\PythonPath

but this doesn't work. Judging by what I see in the registries of old servers at my site, I think it must have worked in Python 1.5, but it doesn't now, as the following shows:

Export the value of the key:
C:\>regedit /E  xxx  HKEY_LOCAL_MACHINE\SOFTWARE\Python\PythonCore\2.6\PythonPath

Display it:
C:\>type xxx
...
@="F:\\Development\\Python26\\Lib;F:\\Development\\Python26\\DLLs;F:\\Developmen
t\\Python26\\Lib\\lib-tk;F:\\Development\\Python26\\Lib\\site-packages\\win32;F:
\\Development\\Python26\\Lib\\site-packages\\pythonwin;c:\\temp"

Note the temporary addition of c:\temp to the end of the path. Now ask Python what it thinks:

C:\>python
Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['', 'C:\\WINNT\\system32\\python26.zip', 'F:\\Development\\Python26\\DLLs', 'F:
\\Development\\Python26\\lib', 'F:\\Development\\Python26\\lib\\plat-win', 'F:\\
Development\\Python26\\lib\\lib-tk', 'F:\\Development\\Python26', 'F:\\Developme
nt\\Python26\\lib\\site-packages', 'F:\\Development\\Python26\\lib\\site-package
s\\win32', 'F:\\Development\\Python26\\lib\\site-packages\\win32\\lib', 'F:\\Dev
elopment\\Python26\\lib\\site-packages\\Pythonwin']
>>>

Not only is c:\temp not in sys.path, even the folders that it has in common with the registry entry are in a different order (eg DLLs and lib), so it's hard to believe that the registry entry has any influence at all on sys.path. Also sys.path has lib\plat-win which I think was introduced about Python 1.5 and I think disappeared again about Python 2.0.

So, why is that registry key there at all? And why does sys.path have the nonexistent plat-win in it, even in Python 3.0? Is it just historical baggage? 

I would like to see the registry key once again working as advertised. I know I can set the pythonpath environment variable, and I also know that environment variables just live in another registry key, but changing that key strikes me as inelegant. Python stuff should live in Software\Python, not in System\CurrentControlSet. 

If the registry key turned out to be a bad idea, it would be illuminating to know why.

--
Paul Keating
The Hague
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