class A: def __len__(self): return 0 print bool(A()) class B: def __len__(self): return False print bool(B()) class C: def __nonzero__(self): return 0 print bool(C()) class D: def __nonzero__(self): return False print bool(D()) class E: def __len__(self): return 1 print bool(E()) class F: def __nonzero__(self): return 1 print bool(F()) class G: def __nonzero__ (self): return 0 def __len__ (self): return 1 print bool(G())