[Distutils] pakage index __getitem__

Phillip J. Eby pje at telecommunity.com
Sun Mar 18 01:25:47 CET 2007

At 07:01 PM 3/17/2007 -0400, Jim Fulton wrote:
>I want to get a list of all of the distributions I can find that
>satisfy a requirement.  I've found the following works:
>    index.obtain(requirement)
>    dists = [d for d in index[requirement.project_name] if d in
>where index is a setuptools.package_index.PackageIndex.
>Is there a better way?

There are other ways, but the above is the simplest and most direct way, 
given your use case.  Normally, performing a resolve() or require() on a 
working set will end up invoking obtain() indirectly, if a requirement 
can't otherwise be met -- this allows network access to be lazy, so it's 
not done unless it's really needed.

>   The obtain call seems to be necessary to
>initialize the index for the given project.

Yes - Environment normally calls 'obtain()' in response to a 'best_match()' 
operation, which is in turn called by a WorkingSet's 'resolve()' 
method.  The idea is that you can subclass Environment (in this case, to 
create a PackageIndex) and override 'obtain()' to find packages in 
locations that are not part of the working set used to create the Environment.

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