已安装的程序包窃取名称空间

Question

I'm developing a package "jw.data" in Python 2.7.9, with a namespace of jw and a package data in in. I have put the canonical

try:
    __import__('pkg_resources').declare_namespace(__name__)
except ImportError:
    from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)

in jw/__init__.py . When I run ./setup.py develop (in setup.py I have put namespace_packages=['jw'] ), then I have "jw" in jw.data.egg-info/namespace_packages.txt . Doing a

import jw.data
import jw.data.model

just works fine. So I guess I have set up the namespace package correctly.

Now I have written a package "jw.util", also in namespace jw , with a package util in it. As soon as I install it, importing jw.data or anything below it fails:

>>> import jw.data
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named data

After uninstalling jw.util it works again.

I used jw.util elsewhere, but not yet in a package within the jw namespace. It looks like jw.util is reserving the jw namespace.

I had the same problem with another namespace. There I noticed the package name in setup.py is just the same as the namespace plus package. I renamed all the packages from "namespace.package x " to "namespace-package x ", and astonishingly enough it worked. I tried the same with jw.util and jw.data , but here that trick doesn't work. And I don't really believe the package name in setup.py has anything to do with the package hierarchy it contains, or has it?

Anyway, anybody got an idea what's going on here?

Answer 1

Seems to be a long-known bug in Python.

But there's a solution in https://github.com/pypa/setuptools/issues/250 :

Put simply, append

;import pkg_resources; pkg_resources.fixup_namespace_packages('')

to the single line in module -nspkg.pth of the competing package in site-packages. The semicolon is required.