[Python-ideas] Trial balloon: adding variable type declarations in support of PEP 484

[Guido van Rossum]

On Thu, Aug 4, 2016 at 8:40 AM, Alexander Belopolsky
<alexander.belopolsky at gmail.com> wrote:
> On Thu, Aug 4, 2016 at 11:22 AM, Guido van Rossum <gvanrossum at gmail.com> wrote:
>> However the presence of a local declaration like 'a: int' would create a
>> local slot for 'a' as if it were assigned to somewhere in the function.
>
> Does this mean that the following code will raise a NameError?
>
> a = None
> def f():
>   a: int
>   a

It will do exactly the same as

a = None
def f():
    if False: a = ...
    a

This raises UnboundLocalError (a subclass of NameError).

> (FWIW, I like the <var>: <type> notation more than any alternative
> proposed so far.)

Me too. :-)

-- 
--Guido van Rossum (python.org/~guido)