gistfile1.txt

>>> from dis import dis
>>> dis('"foo" in {"bar", "tar"}')
  1           0 LOAD_CONST               0 ('foo')
              2 LOAD_CONST               1 (frozenset({'bar', 'tar'}))
              4 COMPARE_OP               6 (in)
              6 RETURN_VALUE
>>> dis('"foo" == "bar" or "foo" == "tar"')
  1           0 LOAD_CONST               0 ('foo')
              2 LOAD_CONST               1 ('bar')
              4 COMPARE_OP               2 (==)
              6 JUMP_IF_TRUE_OR_POP     14
              8 LOAD_CONST               0 ('foo')
             10 LOAD_CONST               2 ('tar')
             12 COMPARE_OP               2 (==)
        >>   14 RETURN_VALUE
>>>

>>> from timeit import timeit
>>> timeit('"foo" in {"bar", "tar"}')
0.026380221999716014
>>> timeit('"foo" == "bar" or "foo" == "tar"')
0.061998130004212726
>>>