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

Paul Moore wrote:

2009/6/18 Lie Ryan <lie.1296@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

Avoiding a nested list comprehension is exactly the motivation for the idea.