[Python-ideas] Inline assignments using "given" clauses

[Cameron Simpson]

On 13May2018 14:23, Chris Angelico <rosuav at gmail.com> wrote:
>On Sun, May 13, 2018 at 2:05 PM, Cameron Simpson <cs at cskk.id.au> wrote:
>> Could someone point me to a post which nicely describes the rationale behind
>> its rejection?  I'm sure there's one in the many in this discussion but I've
>> not found it yet.
>
>https://www.python.org/dev/peps/pep-0572/#special-casing-conditional-statements
>https://www.python.org/dev/peps/pep-0572/#alternative-spellings
>
>I'm not sure which version you're looking at, so there's the rejections of 
>both.

I meant the latter, but I'd already looked at that part of the PEP and found 
its explaination... unfulfilling. It says:

  EXPR as NAME:

    stuff = [[f(x) as y, x/y] for x in range(5)]

  Since EXPR as NAME already has meaning in except and with statements (with
  different semantics), this would create unnecessary confusion or require
  special-casing (eg to forbid assignment within the headers of these
  statements).

All you need to disambiguate, say:

  with expr as expr_as as with_as:

is to require parentheses for (expr as exp_as) if someone wanted that 
complications (assuming that is even necessary - it seems unambiguous to my eye 
already, unless the token lookahead requirement in Python's grammar prevents 
that.

So I'd hoped for a post to the list discussing this aspect and outlining why it 
was considered unsatisfactory.

Cheers,
Cameron Simpson <cs at cskk.id.au>