[Python-Dev] assignment expressions: an alternative proposal

[Chris Angelico]

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:
>> On Tue, Apr 24, 2018 at 11:05:57AM -0400, Yury Selivanov wrote:
>>
>>> Well, `my_func(a=(b:=foo))` or `my_func(b:=foo)` are also barely
>>> readable to my eye.
>>
>> 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.

ChrisA