[Python-Dev] assignment expressions: an alternative proposal

[Yury Selivanov]

On Tue, Apr 24, 2018 at 10:49 AM, Paul Moore <p.f.moore at gmail.com> wrote:
[..]
>>> 3. Most importantly: it is *not* allowed to mask names in the current
>>> local scope.
>>
>> While I agree this would be unambiguous to a computer, I think for
>> most humans it would be experienced as a confusing set of arcane and
>> arbitrary rules about what "=" means in Python.
>
> Also, there's the ambiguity and potential for misreading in the
> opposite direction (accidentally *reading* = as == even though it
> isn't):
>
> if (diff = x - x_base) and (g = gcd(diff, n)) > 1:
>      return g

Since 'diff' and 'g' must be new names according to rule (3), those
who read the code will notice that both were not previously bound.
Therefore both are new variables so it can't be a comparison.

Yury