Python is DOOMED! Again!

Ian Kelly ian.g.kelly at
Thu Jan 22 23:12:30 CET 2015

On Thu, Jan 22, 2015 at 3:08 PM, Ian Kelly <ian.g.kelly at> wrote:
> On Thu, Jan 22, 2015 at 2:56 PM, Emile van Sebille <emile at> wrote:
>> I've been lightly scanning and following the PEP 484 discussion, and one
>> point I don't think I've seen mentioned is how you might hint a function
>> that accepts different types, eg:
>> def adder(a,b): return a+b
>> This is one of the pythonic idioms that help with polymorphic functions.  Is
>> there a proposal for providing hinting for these?
> You can use TypeVar for that.
> T = TypeVar('T')
> def adder(a: T, b: T) -> T:
>     return a + b
> I'm not thrilled about having to actually declare T in this sort of
> situation, but I don't have a better proposal.

Hmm, but also that hinting doesn't cover cases like adder(12, 37.5)
where two different types can be passed, and the return type could be
either. I think for full generality you would just have to forgo
hinting on this function.

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