On 13May2018 14:23, Chris Angelico <ros...@gmail.com> wrote:
On Sun, May 13, 2018 at 2:05 PM, Cameron Simpson <c...@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 <c...@cskk.id.au>
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