[Python-Dev] (name := expression) doesn't fit the narrative of PEP 20

[Terry Reedy]

On 4/25/2018 8:20 PM, Chris Angelico wrote:
> On Thu, Apr 26, 2018 at 10:11 AM, Yury Selivanov
> <yselivanov.ml at gmail.com> wrote:
>> Just yesterday this snippet was used on python-dev to show how great the
>> new syntax is:
>>
>>            my_func(arg, buffer=(buf := [None]*get_size()), size=len(buf))

What strikes me as awful about this example is that len(buf) is 
get_size(), so the wrong value is being named and saved. 
'size=len(buf)' is, in a sense, backwards.

buflen  = get_size()
my_func(arg, buffer = [None]*buflen, size=buflen)

Is standard, clear Python code.  I do not see that
my_func(arg, buffer=[None]*(buflen:=get_size()), size=buflen)
is an improvement.

-- 
Terry Jan Reedy