Being pedantic: This isn't true in Haskell, because list comprehensions can use pattern matching, while map+filter can't.

  heads :: [[a]] -> [a]
  heads xs = [y | (y:ys) <- xs]

  -- heads [[1],[],[2,3]] == [1,2]

Doing the above using maps and filters looks very different:

  heads' = map head . filter (not . null)

Python doesn't really support Haskell-like pattern matching, so the above doesn't apply.