Python Sanity Proposal: Type Hinting Solution

Chris Angelico rosuav at
Fri Jan 23 18:11:18 CET 2015

On Sat, Jan 24, 2015 at 12:23 AM, Fetchinson .
<fetchinson at> wrote:
> In any case, I'm pretty sure it was said before, but I can't really
> find it anywhere, can someone tell me what the rationale is for
> *function signature* type hinting?
> I totally get type hinting in general, but why does it have to be in
> the function signature? Any reason for that specifically?

Is there any particular reason for the number of arguments to be part
of the function signature? I totally get the notion of declaring how
many arguments a function takes, but why does it have to be in the
function signature?

Data types are just as much a part of that signature as argument count
is. You could argue that the function's return type isn't part of
that, but that's about it.

> If there is a pep for it, people will use it, so the fact that
> it is optional is irrelevant...

Function annotations were introduced in 2006 (Python 3.0) with PEP 3107:

They were optional then, they are still optional now. Have you been
overrun with them for the past decade? If not, why do you expect now
to be?


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