Python: split a list based on a condition?

Question

What\'s the best way, both aesthetically and from a performance perspective, to split a list of items into multiple lists based on a conditional? The equivalent of:

Answer 1

If you insist on clever, you could take Winden's solution and just a bit spurious cleverness:

def splay(l, f, d=None):
  d = d or {}
  for x in l: d.setdefault(f(x), []).append(x)
  return d