Temporary variables in list comprehensions

Chris Angelico rosuav at gmail.com
Sun Jan 8 23:09:33 EST 2017


On Mon, Jan 9, 2017 at 2:53 PM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> [(tmp, tmp + 1) for x in data for tmp in [expensive_calculation(x)]]
>
>
> I can't decide whether that's an awesome trick or a horrible hack...

A horrible hack on par with abusing a recursive function's arguments
for private variables. Much better would be to refactor the append
part:

def this_and_one(value):
    return value, value + 1

[this_and_one(expensive_calculation(x)) for x in data]

ChrisA


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