[Python-Dev] assignment expressions: an alternative proposal

[Yury Selivanov]

On Tue, Apr 24, 2018 at 11:58 AM, Chris Angelico <rosuav at gmail.com> wrote:
> On Wed, Apr 25, 2018 at 1:49 AM, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
>> On Tue, Apr 24, 2018 at 11:34 AM, Steven D'Aprano <steve at pearwood.info> wrote:
[..]
>>> There's no advantage to using binding-expressions unless you're going to
>>> re-use the name you just defined, and that re-use will give you a hint
>>> as to what is happening:
>>>
>>>     my_func(arg, buffer=(buf := [None]*get_size()), size=len(buf))
>>
>> Again, this is very subjective, but this code would fail my code review :)
>>
>> Don't you find
>>
>>   buf = [None] * get_size()
>>   my_func(arg, buffer=buf, size=len(buf))
>>
>> to be more readable?
>
> Only if 'buf' is going to be used elsewhere. I'd be looking down below
> for some other use of 'buf'. Technically the same could be true of the
> inline assignment, but it makes more sense for a "this statement only"
> name binding to be within that statement, not broken out and placed
> above it as another operation at equal importance.

Well, you can use empty lines to visually indicate that 'buf' is
related to the call.

Moreover, 'buf' is still available to the code below that code and
sometimes be used there. You can't tell for sure until you glance over
the entire file/function. PEP 572 does not implement any sort of
sub-scoping.

Yury