Support __main__

[refi64]

Right now, it says the module can't be found.

[JukkaL]

Ah yes, I stumbled into this a while ago myself. Thanks for reporting this!

[ddfisher]

@kirbyfan64 I know it's been a while, but can you be more specific about the issue you ran into here?

[refi64]

I think it was import __main__.

[gvanrossum]

If you're talking about code that imports __main__, I can't repro. E.g.

mypy -c 'import __main__'

passes without errors.

[ErikBjare]

@gvanrossum Put the import __main__ in a file then run mypy test_main.py.

The following will happen:

test_main.py:1: error: Cannot find module named '__main__'
test_main.py:1: note: (Perhaps setting MYPYPATH would help)

Interesting that mypy -c 'import __main__' works.

[gvanrossum]

FWIW this is because when you pass module filenames (i.e. *.py) on the command line the module name is derived from the filename. So mypy test_main.py sets the module name to test_main. With -c the module name is always set to __main__. The module name is also set to __main__ if you pass a file whose extension isn't .py (or .pyi).

So I'm not even sure this counts as a bug. Certainly the legit use cases for importing __main__ are pretty limited, and mypy probably shouldn't assume it has any particular attributes.

[JukkaL]

What about __main__ in a package, to run a package as a program?

[gvanrossum]

That's different, there will always be a `__main__.py` in that case and it's not toplevel.

[gvanrossum]

Is there a compelling use case?