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. Even if f() is not a function such as [x + 1 for x in l if x + 1 > 0] it looks ugly since we're repeating ourself. We can work around it like this: [y for y in (f(x) for x in l) if y > 0] but then we have an unnecessary nested loop comprehension. I'm suggesting about something like: [f(x) for x in l if @ > 0] where @ is the result of the listcomp's expression (i.e. f(x)) Personally, I don't like the use of symbols like @, as python is not perl. I'm still thinking of a better syntax/approach and is open for suggestion. What do you guys think?