[Python-ideas] FW: Map-then-filter in comprehensions

[Chris Angelico]

On Wed, Mar 9, 2016 at 5:32 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
> On 03/08/2016 10:27 AM, Chris Angelico wrote:
>
>> Implement that, and people will ask why they can't then unroll that:
>>
>> def <listcomp>():
>>      result = []
>>      for x, y in some_iterable:
>>          if x+y as z > 10: # SyntaxError
>>              result.append(z)
>>      return z
>
>
> Seriously?
>
> def blah():
>     result = []
>     for x, y in some_iterable:
>         z = x + y
>         if z > 10:
>             result.append(z)
>     return result  # not z
>
> That doesn't seem too difficult.  ;)

Ah yes, but that's not how you've written it in the comprehension. You
wrote it with 'as'. Believe you me, people WILL expect that outside of
comprehensions. Otherwise, you have to explain why a name binding is
legal in a condition in a comprehension, but not in any other
expression.

ChrisA