Kent Johnson wrote:
> I am building a list like this:
>
> tree = []
> for top in tops:
> l2 = level2(top)
> if l2:
> tree.append((top, l2))
>
> I would really like to turn this into a list comprehension:
>
> tree = [ (top, level2(top)) for top in tops if level2(top) ]
>
> but the call to level2() is expensive enough that I don't want to repeat
> it. Is there any way to do this or am I stuck with the (IMO ugly) loop form?
>
Just playing around here, but would this work and be better????
tree = [ pair for pair in [ (top, level2(top)) for top in tops ]
if pair[1] ]
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