[Python-Dev] Assignment expression and coding style: the while True case

Chris Angelico rosuav at gmail.com
Wed Jul 4 20:36:38 EDT 2018

On Thu, Jul 5, 2018 at 10:33 AM, Victor Stinner <vstinner at redhat.com> wrote:
> 2018-07-05 2:15 GMT+02:00 Chris Angelico <rosuav at gmail.com>:
>> On Thu, Jul 5, 2018 at 10:03 AM, Victor Stinner <vstinner at redhat.com> wrote:
>>> On the 3360 for loops of the stdlib (*), I only found 2 loops which
>>> would benefit of assignment expressions.
>>> It's not easy to find loops which:
>>> - build a list,
>>> - are simple enough to be expressed as list comprehension,
>>> - use a condition (if),
>>> - use an expression different than just a variable name as the list
>>> value (value appended to the list).
>> Are you implying that the above conditions are essential for
>> assignment expressions to be useful, or that this defines one
>> particular way in which they can be of value?
> Hum, maybe I wasn't specific enough. I'm looking for "for loops" and
> list comprehensions in stdlib which *can be* written using assignment
> expression, like:
>    [var for ... in ... if (var := expr)].
> I'm not discussing if such change is worth it or not. I just counted
> how many for loops/list comprehensions *can* be modified to use
> assingment expressions in the stdlib.
> Maybe I missed some loops/comprehensions, and I would be happy to see
> more examples ;-)

Cool. So you're looking for ones that fit a particular pattern that
can benefit, but there are almost certainly other patterns out there.
Just making sure that you weren't trying to say "out of 3360 loops,
exactly 3358 of them absolutely definitely cannot be improved here".


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