Support imports of namespaces in python>=3.3 (modules without __init__.py files)

[mishas]

Python 3.3 introduced "Implicit Namespace Packages" (based on PEP-420), which states the following:
"Native support for package directories that don’t require __init__.py marker files [...]".

In other words, if I have the following file structure (without any __init__.py files whatsoever):

foo/
    bar/
        baz.py
blah.py

And the content of blah.py is from foo.bar import baz; print(baz), then python3.5 ./blah.py will successfully output: <module 'foo.bar.baz' from '/tmp/foo/bar/baz.py'>.

The problem is, that pylint ./blah.py outputs:
E: 1, 0: Unable to import 'foo.bar' (import-error)

I tried to manipulate sys.path (from init-hook of my .pylintrc) in any which way, and nothing seemed to help except for adding the __init__.py files everywhere :(.

[PCManticore]

Agree that this would be nice to have, but not sure when this will happen.

[srikanth-viswanathan]

This would be great to have. Is this just a minor enhancement? Out of curiosity, where would the change have to be made?

[kstrauser]

For my organization, it's not minor but a real showstopper. We use lots of namespace packages and are moving to the new implicit namespace package layout, so we can't use pylint in the mean time. Is this something a motivated would-be contributor with no prior pylint experience could reasonably fix?

[moylop260]

@kstrauser
I had a similar issue with import check but I can use pylint with pylint... --disable=import-error
FYI You can try it to use pylint with other checks that works but disabling the checks that don't work for you

[kstrauser]

@moylop260 But I use import errors. :-/ I've temporarily switched to flake8 but I'd much prefer pylint on the CI server.

[moylop260]

Flake8 don't have import-error is the same if you use pylint disabling it
But is a good choice too!

[moylop260]

A big problem with use import-error in the CI is that many times you need a speed-up result of lint checks, but for this check (and just this check) you will need install all depends, then could be slower the result of this build.

[PCManticore]

@kstrauser, this would probably be a bit difficult, since it will require modifications through astroid as well (the inference engine of Pylint). But if you want to tackle it, I can help you with the details.

[kstrauser]

@PCManticore Thanks, after looking at it that might be outside my current resource availability. I'm going to keep that in mind as a possibility, though.

[PCManticore]

Let's fix this before the next release. I'm assigning to me for now, but if anyone wants to chime in and help, I wouldn't mind.

[PCManticore]

For the record, I started implementing this feature. It's pretty much work in progress, but you can check these two branches https://github.com/PyCQA/pylint/commits/namespace_package and https://github.com/PyCQA/astroid/commits/namespace_package. It doesn't support Python 3.3 though, it is a bit cumbersome to support it, but if someone needs it, say it now.