[Python-ideas] A PEP on introducing variables on 'if' and 'while'

[Juancarlo Añez]

> The only difference is that the `except` block implicitly unbinds the
> variable when the block ends.
>

Mmmm. Good to know, because that means that the semantics are the same,
except...

>
>     while (condition := expression) as flag:
>         ...
>

Ah! Are the parenthesis necessary there?


Accepting "while/if as name" would remove much (but not all) of the
> motivation for assignment expressions, while accepting assignment
> expressions would make a dedicated while/if as name syntax unnecessary.
>

Most of the arguments in favor of ':=' have been through examples of
generators in which the introduced name is used within, with the if/while
case often forgotten.

There can be cases in which combining both syntaxes is useful:

x = None
while compute(x := v for v in next_series_value(x)) as comp:
    ...
    x = comp




> Like it or not, I expect that they will be seen as competing PEPs, not
> independent ones.



Finding a real-world example of something like the above synthetic example
would be in favor of the orthogonality.

-- 
Juancarlo *Añez*
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