[Python-ideas] Accessing the result of comprehension's expression from the conditional

[Paul Moore]

2009/6/18 Lie Ryan <lie.1296 at gmail.com>:
> In list/generator comprehension, currently we have no way to access the
> result of the expression and have to write something like this:
>
> [f(x) for x in l if f(x) > 0]
>
> if f() is heavy or non-pure (i.e. have side effects), calling f() twice
> might be undesirable.

[y for y in (f(x) for x in l) if y > 0]

But as Aahz says, if it's too complex, use an explicit loop. Not
everything needs to be a one-liner.

Paul