[Python-Dev] Informal educator feedback on PEP 572 (was Re: 2018 Python Language Summit coverage, last part)

[Eric Fahlgren]

On Wed, Jun 27, 2018 at 9:27 AM Paul Moore <p.f.moore at gmail.com> wrote:

> From my reading, PEP 572 takes the position that "parent local
> scoping" is what people expect from assignment expressions *in
> comprehensions* and it's useful enough that there is no reason not to
> make that the behaviour. The behaviour isn't generally useful enough
> to be worth exposing as a primitive (it's not even useful enough for
> the PEP to give it an explicit name!) so it's just a special case for
> assignment expressions in comprehensions/generators.
>

​So, my interpretation is that it will behave like this?

x = 2
y = [x := 3 for i in range(1)]
print(x)
3

def f():
    x = 4
    y = [x := 5 for i in range(1)]
    print(x)
f()
5

class C:
    x = 6
    y = [x := 7 for i in range(1)]
    print(x)
C()
6
print(x)
7​
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