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[Python-Dev] assignment expressions: an alternative proposal

Yury Selivanov yselivanov.ml at gmail.com
Tue Apr 24 11:46:57 EDT 2018 
On Tue, Apr 24, 2018 at 11:28 AM, Chris Angelico <rosuav at gmail.com> wrote:

> On re-thinking this, I think the distinction IS possible, but (a) only
> in function/class scope, not at global; and (b) would be defined in
> terms of lexical position, not run-time. For instance:
>
> def f():
>     (a = 1) # Legal; 'a' has not been used yet
>     a = 2 # doesn't change that
>
> def f(a):
>     (a = 1) # Invalid - 'a' has been used already
>
> def f():
>     while (a = get_next()): # Legal
>         ...

Now *this* is a weird rule. Moving functions around files would become
impossible.

Please experiment with my reference implementation, it already
implements my proposal in full. Loops and inline assignments work as
expected in it.

Yury
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