[tahoe-dev] startup error after upgrade

Zooko Wilcox-O'Hearn zooko at zooko.com
Fri Mar 29 22:06:48 UTC 2013


I thought the design flaw in question was:

When you "import foo", and there are multiple modules named "foo" in your
filesystem, then which specific module you get is determined by a list of
directories, each of which can contain multiple modules. Therefore, when
you add a directory to the front of that list you are prioritizing *all* of
the modules in that directory over any other modules by the same name in
any other directories. Therefore, if a single directory contains both a
module you want to import and a module that you mustn't import (because it
name-collides with another module that you want to import), then you have
to make sure the *other* directory is earlier than this one on the list. If
there is a cycle of such dependencies, then it is impossible to import all
the modules that you require.

That particular design flaw is built into the Python import mechanism, and
would still prevent you from importing the modules if there were no
distutils, pkg_resources, or setuptools on your system.

Regards,

Zooko
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