[Distutils] DWIM installation with setuptools

Phillip J. Eby pje at telecommunity.com
Sat Feb 11 22:22:32 CET 2006

At 03:53 PM 2/11/2006 -0500, Jim Fulton wrote:
>Phillip J. Eby wrote:
>>Regarding #1, my first thought is that the most backward-compatible thing 
>>to do would be to extend the current PYTHONPATH with the one that was in 
>>effect when the script was installed.  Thus, if you set a PYTHONPATH with 
>>the intent of overriding something, your wish will still be 
>>granted.  (The 'site' module eliminates duplicate paths, so sys.path 
>>isn't elongated in the case of duplication.)  You can still break the 
>>script by setting PYTHONPATH to something that creates a version 
>>conflict, but you could do that anyway.
>This is close, but too implicit, IMO.  I'd rather have an
>easy_install option (command-line and config file) to specify the
>path that the wrappers should set.
>>The main question, then, is whether this path-freezing should be done by 
>>default, or whether it should be an option.  My inclination is to make it 
>>a user-controlled option, at least at first.
>Yup.  IMO, this option shouldn't be boolean, but, rather, should
>specify the paths to add explicitly.

I don't really like that idea; it seems too easy to foul it up by not 
having the right value(s), since easy_install effectively uses the existing 
setting to determine whether an installed thing has all its dependencies 
met.  If you are going to be wrapping easy_install in something else 
anyway, you can just set the PYTHONPATH before the call.  That seems a lot 
safer to me, because then easy_install will be evaluating dependencies 
properly in the context of the desired PYTHONPATH value.

I think what I'm going to have to do to implement this on windows is have 
an additional foo-script.env file to hold the PYTHONPATH and any other 
special options.  That way, I only have to write or delete that extra file, 
and everything else works the same.  (For 'nix, I'll only need to prepend a 
/bin/sh header to the script.)

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