On Fri, Sep 12, 2014 at 8:38 AM, Thomas Heller <thel...@ctypes.org> wrote:
> While trying to add support for PEP420 implicit namespace packages
> support to py2exe's modulefinder, I noticed something strange.
>
> I'm using the wheezy.template and zope.interface packages for my tests,
> they are installed with pip.
>
> pip creates wheezy.template-0.1.155-py3.4-nspkg.pth and
> zope.interface-4.1.1-py3.4-nspkg.pth files that are not present in the
> package sources. The contents is like this:
>
> """
> import sys,types,os; p = os.path.join(sys._getframe(1).f_locals['sitedir'],
> *('wheezy',)); ie = os.path.exists(os.path.join(p,'__init__.py')); m = not
> ie and sys.modules.setdefault('wheezy',types.ModuleType('wheezy')); mp = (m
> or []) and m.__dict__.setdefault('__path__',[]); (p not in mp) and
> mp.append(p)
> """
>
> What is the purpose of these files? (The packages seem to work also
> when I delete these files; which is what I expected from implicit
> namespace packages...)
>
>
> These .pth-files have the effect that they insert the modules 'wheezy'
> and 'zope' into sys.modules, even when I don't import anything
> from the packages. However, these modules are IMO damaged, they
> only have __doc__, __name__, and __path__ attributes (plus __loader__
> and __spec__ in Python 3.4, both set to None).
>
> Reloading the package in Python 3.3 raises an error, and
> importlib.find_loader("zope") also:
>
>>>> sys.modules["zope"]
> <module 'zope'>
>>>> import zope
>>>> zope
> <module 'zope'>
>>>>
>>>> imp.reload(zope)
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "C:\Python33\lib\imp.py", line 276, in reload
> module.__loader__.load_module(name)
> AttributeError: 'module' object has no attribute '__loader__'
>>>>
>>>> importlib.find_loader("zope", None)
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "C:\Python33\lib\importlib\__init__.py", line 64, in find_loader
> loader = sys.modules[name].__loader__
> AttributeError: 'module' object has no attribute '__loader__'
>>>>
>
> Trying the same in Python 3.4, behaviour is quite similar although
> imp.reload() 'fixes' that package:
>
>>>> import sys
>>>> sys.modules["zope"]
> <module 'zope'>
>>>> dir(sys.modules["zope"])
> ['__doc__', '__loader__', '__name__', '__package__', '__path__', '__spec__']
>>>> sys.modules["zope"].__spec__
>>>>
>>>> import zope
>>>> zope
> <module 'zope'>
>>>> import importlib.util
>>>> importlib.util.find_spec("zope", None)
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "C:\Python34\lib\importlib\util.py", line 100, in find_spec
> raise ValueError('{}.__spec__ is None'.format(name))
> ValueError: zope.__spec__ is None
>>>> import imp
>>>> imp.reload(zope)
> <module 'zope' (namespace)>
>>>> importlib.util.find_spec("zope", None)
> ModuleSpec(name='zope', loader=None, origin='namespace',
> submodule_search_locations=_NamespacePath(['C:\\Python34\\lib\\site-packages\\zope']))
>>>>
Hi Thomas,
I've dealt with this issue myself extensively in the past, but it's
been a while so I might have to give it a bit of thought before I
comment more on detail (if no one else does first).
But I don't think (unless there's something new I don't know about)
those come directly from pip. Rather, they are created by setuptools.
The issue here is that before Python had any built-in notion of
namespace packages, namespace packages were a feature in setuptools,
and this was the hack, I suppose, that allowed it to work.
Unfortunately as different versions of Python have grown different
levels of support for namespace packages over the years, the
setuptools hack is still the implementation of the concept that will
work on the broadest range of Python versions (and I definitely know
zope.interface has been using it going far back).
That said, I've been meaning to try to figure out some way of
supporting all three forms of namespace packages in a way that is
interfering. As I said, I've had problems with this myself :/
Erik
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