3 ms·

I couldn't resist. add = lambda a, b: add(a ^ b, (a & b) << 1) if b else a

• recursive 10y ago
  And if you need to handle negatives: def add(a, b): while a and b: if a ^ b < 0: (a, b) = (a & ~b, b & ~a) (a, b) = (a ^ b, (a & b) << 1) return a or b