support mypy statically type check

[zchee]

We want to easily maintenance to the source.
I think mypy type check is a very good feature and approach.

[blueyed]

You want to run this on CI/Travis?

[zchee]

@blueyed Ah, just only for easily maintenance for developers. Not for testing.
I mean, introduction of a pseudo type checking.

[blueyed]

So you mean to use function annotations in the source code?

[zchee]

@blueyed Yes, like

x = 1 # type: int
x = 1.0 # type: float
x = True # type: bool
x = "test" # type: str

x = [1] # type: List[int]
x = set([6, 7]) # type: Set[int]

I don't know Python community; Use mypy is a bad idea?

[Mic92]

mypy is currently getting more and more attention by the community, so it is a good to have support for that.