try: a = [1, 2, 3] a.index(999) exit(1) except ValueError: pass # test some python magics class A: def __init__(self): self.d = {} def __getitem__(self, index): return self.d[index] def __setitem__(self, index, value): self.d[index] = value def __contains__(self, index): return index in self.d def __delitem__(self, index): del self.d[index] a = A() a['1'] = 3 assert '1' in a assert '2' not in a assert a['1'] == 3 del a['1'] assert '1' not in a # slice extras class A: def __getitem__(self, index): return index assert slice(1, 2, None) == slice(1, 2, None) assert slice(1, 3, None) != slice(1, 2, None) assert A()[1] == 1 assert A()[1:2, 3] == (slice(1, 2, None), 3) assert A()[1:2, 3:4] == (slice(1, 2, None), slice(3, 4, None)) assert A()[1:2, 3:4, 5] == (slice(1, 2, None), slice(3, 4, None), 5) assert A()[:, :] == (slice(None, None, None), slice(None, None, None)) assert A()[::, :] == (slice(None, None, None), slice(None, None, None)) assert A()[::, :2] == (slice(None, None, None), slice(None, 2, None)) assert A()['b':'c':1, :] == (slice('b', 'c', 1), slice(None, None, None)) assert A()[1:2, :A()[3:4, ::-1]] == (slice(1, 2, None), slice(None, (slice(3, 4, None), slice(None, None, -1)), None))