Confusion on return type of difflib.get_closest_matches

[deveshks]

There is a mismatch between the return type mentioned in the docs of difflib.get_close_matches (List[str]) vs what is mentioned in typeshed source code (List[Sequence[_T]])

This was observed when I was trying to add type annotations to https://github.com/pypa/pip/blob/master/src/pip/_internal/commands/__init__.py#L103

[McSinyx]

As you mentioned in the linked PR, this is a duplicate of GH-2067 (and python/mypy#1965). Generally it's not a good idea to re-file an issue. In this particular case, it is possible to cast the return value to List[str] however.

[deveshks]

Hi @McSinyx

I had a discussion with @pradyunsg and he mentioned that #2067 is in fact definitely a different bug, hence I have filed this bug.

[pradyunsg]

s/not a different/definitely a different/

[JelleZijlstra]

This does sound like the same issue as #2067. As I said there, it's fixable with an overload, and I just submitted #3908 doing that.

Here's the relevant behavior:

In [10]: difflib.get_close_matches('x', ['y', 'zx'])                                                                                                                                              
Out[10]: ['zx']

In [11]: difflib.get_close_matches((1, 2, 3), [(1, 2), (1, 2, 3, 4)])                                                                                                                             
Out[11]: [(1, 2, 3, 4), (1, 2)]

[deveshks]

Thanks @JelleZijlstra for the quickaround and the fix. Really appreciate it 😄