Mypy doesn't recognize objects implementing __iter__ as being Iterable

[rowillia]

This might be in the category of issues around supporting protocol methods as a whole.

test_iter.py:

from typing import Iterator

class Foo(object):
    def __iter__(self) -> Iterator[int]:
        yield 1
        yield 2

for x in Foo():
    print(x)

$ mypy test_iter.py
test_iter.py:8: error: Iterable expected

[afrieder]

This happens because Iterable is a distinct class, not an interface. To indicate to Python/Mypy that Foo is Iterable, you have to directly subclass Iterable:

from typing import Iterator, Iterable

class Foo(Iterable):
    ....

then the rest of your code correctly type-checks.

[gvanrossum]

True, but we would all wish that it could work. python/typing#11

I don't think we need to keep this open as a separate issue though.