[Distutils] Importable wheels using distlib/distil

PJ Eby pje at telecommunity.com
Fri Mar 29 21:42:08 CET 2013

On Fri, Mar 29, 2013 at 3:55 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> No, mutating sys.path for versioned imports is a broken design. You
> end up with two possibilities:
> * If you append, then you can't override modules that have a default
> version available on sys.path. This is not an acceptable restriction,
> which is why pkg_resources doesn't do it that way
> * If you prepend, then you have the existing pkg_resources failure
> mode where it can accidentally shadow more modules than intended. This
> is a nightmare to debug when it goes wrong (it took me months to
> realise this was why a system install of the main application I work
> on was shadowing the version in source checkout when running the test
> suite or building the documentation).
> The correct way to do it is with a path hook that processes a special
> "<versioned-packages>" marker label in sys.path (probably placed after
> the standard library but before site-packages by default). Any mounted
> directories would be tracked by that path hook, but never included
> directly in sys.path itself.

How is that different from replacing "<versioned-packages>" with the
path of the versioned package being added?

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