[tahoe-dev] startup error after upgrade

Zooko Wilcox-O'Hearn zooko at zooko.com
Tue Apr 2 16:06:12 UTC 2013

On Tue, Apr 2, 2013 at 1:41 AM, Daira Hopwood (formerly David-Sarah) <
david-sarah at jacaranda.org> wrote:

> But the original assumption was that you would never have multiple
> versions of a single
> package installed. That is, if you wanted to install a new version, you'd
> uninstall any
> older version (and put up with any backward compatibility issues).

I think you're right.

> In that case, there
> would be no "module that you mustn't import" in the same place as a
> "module you want to
> import".

Well... you could also have other name-collisions...

> setuptools promises to allow you to install multiple versions, and that's
> what fails to
> work.

Okay, you're right, but the reason it fails is because that is impossible
(for the general case) while maintaining backward-compatibility with
builtin import mechanism which prioritizes multiple modules into the same
priority bucket based on the directory they are in. If I recall correctly,
which is dubious at this point, setuptools itself installs each new module
in its own directory (or zip file), so only modules that were installed
with non-setuptools installers can run afoul of this limitation in the
non-setuptools import mechanism.

By the way, I heard that at this year's packaging summit at Pycon, the
maintainers of setuptools and distribute agreed to combine efforts and make
a new series of setuptools, maintained, I guess, by the people responsible
for the "distribute" fork.


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