Issue with builtins.slice Signature

[froomzy]

I have been trying mypy out, and I am hitting something I don't understand. I have the following line of code:

NZD = Currency(name='New Zealand Dollars', abbreviation='NZD', slice=slice(3, None, None), format='NZ${price:.2f}')

When I run mypy over it I get the following error (in python3.5 virtualenv):

mypy --strict-optional -p lists
lists\constants.py:13: error: Argument 2 to "slice" has incompatible type None; expected "int"

It seems that slice has a type signature of slice(int, int, int), but to get the behavior I want (give me everything in the string after the third character) I need to pass in a None. I think they should be Optional[int]s rather than ints.

Hopefully that makes sense.

[gvanrossum]

I think you can just submit a PR to fix this.

I expect that the attributes should also be Optional[int]?

There are also two issues discussing bigger changes to slice, but I think they are somewhat controversial:

• Unexpected "error: Slice index must be an integer or None" mypy#2410
• builtins.slice should be generic typing#159

[froomzy]

Righto. I have not done a pull request before, so time to go learn about that.

[JelleZijlstra]

Looks like this can be closed since the PR was merged.

[gvanrossum]

Which makes me think, reviewers should be more careful to edit the commit summary, message body, and auto-close text (preferably "fixes #x" or "closes #x" -- the latter if it's not really a fix but e.g. a feature request).