Using the variable type annotation syntax as a placeholder in a nonlocal scope?

[Kirill Balunov]

Any suggestions? Thank you.

With kind regards, -gdg

On Dec 20, 2017 22:43, "Kirill Balunov" <kirillbalunov at gmail.com> wrote:

> I've asked the same question on StackOverflow, but it seems to me that it
> is opinion based and will be ignored. So I ask for advice here:
>
> Since PEP 526 -- Syntax for Variable Annotations
> <https://www.python.org/dev/peps/pep-0526/>  was approved, in Python 3.6+
> it is possible to provide type hint information in the form *x: int*,
> also the PEP says "However, annotating a local variable will cause the
> interpreter to always make it local to the scope and leaves the variable
> uninitialized". Therefore in Python 3.6+ it is syntactically legal to
> write:
>
> def outer():
>     x: int
>     def inner():
>         nonlocal x
>         x = 10
>     inner()
>     print(x)
>
> while the above snippet is semantically more equivalent to:
>
> def outer():
>     #x
>     def inner():
>         nonlocal x
>         x = 10
>     inner()
>     print(x)
>
> Which is obviously a *SyntaxError: no binding for nonlocal 'x' found`*,
> sorry for the pun. Also there is nothing said about this style in PEP 8 and
> Python 3.6 docs. So should I consider this as a bug, or an implementation
> detail (side effect), or a wart, or a feature?
>
> To clarify the purpose of the question - we can not come to a consensus
> and I would like to hear your opinion and possible pitfalls, if any, if we
> choose to use this form in our codebase.
>
> With kind regards, -gdg
>
>
>