Why is if True slower than if 1?

True and False are not keywords in Python 2.

They must resolve at runtime. This has been changed in Python 3

Same test on Python 3:

>>> timeit.timeit('test1()',setup="from __main__ import test1", number=10000000)
2.806439919999889
>>> timeit.timeit('test2()',setup="from __main__ import test2", number=10000000)
2.801301520000038
>>> timeit.timeit('test3()',setup="from __main__ import test3", number=10000000)
2.7952816800000164
>>> timeit.timeit('test4()',setup="from __main__ import test4", number=10000000)
2.7862537199999906

Time error is in 1%, which is acceptable.