PEP 526 - var annotations and the spirit of python
Gregory Ewing
greg.ewing at canterbury.ac.nz
Thu Jul 5 01:34:55 EDT 2018
Steven D'Aprano wrote:
> but the type checker should infer that if you assign None to a variable
> which is declared int, you must have meant Optional[int] rather than just
> int.
This seems to be equivalent to saying that *all* types are
Optional, in which case what point is there in having Optional
at all?
> Indeed, that's often the best way, except for the redundant type hint,
> which makes you That Guy:
>
> x: int = 0 # set x to the int 0
But you've shown in an earlier example that such a hint is
*not* always redundant, e.g.
x = 0
x = 2.5
is legal and useful, whereas
x: int = 0
x = 2.5
ought to be a type error.
--
Greg
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