[Python-ideas] More power in list comprehensions with the 'as' keyword

Terry Reedy tjreedy at udel.edu
Thu Aug 28 22:37:20 CEST 2008

Mathias Panzenböck wrote:
> Marcin 'Qrczak' Kowalczyk schrieb:
>> 2008/8/28 Cesare Di Mauro <cesare.dimauro at a-tono.com>:
>> [stripped | l <- text.split('\n'), let stripped = l.strip(), stripped != '']
>> Python borrowed 2 out of 3 kinds of list comprehension constructs.
> so maybe?
> [stripped for l in text.split('\n') if stripped != '' let stripped = l.strip()]

To parallel the Haskell-ish example, this should be

[stripped for l in text.split('/n') stripped as l.strip() if stripped != '']

but the clause has 'as' in the middle instead of at the beginning, 
making it hard to parse.  Haskell used commas

[stripped for l in text.split('/n'), stripped as l.strip(), if stripped 
!= '']

but I think this would conflict with Python's other comma usage.  Most 
feasible, I think, would be

[stripped for l in text.split('/n') with stripped as l.strip() if 
stripped != '']

This corresponds to the multi-statement for loop version

for l in text.split('\n'):
   stripped = l.strip()
   if stripped != '':

with 'stripped = l.strip()' replaced by 'with stripped as l.strip()'. 
If other use cases were presented that could not be more easily written 
otherwise, as with the re.split() version, I might at least be neutral 
on this.

Terry Jan Reedy

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