Why is “not” faster than “bool()” in Python (or, speed of Python functions vs. statements)?

Question

I made an interesting observation the other day. I was experimenting with various ways to get the \"truthiness\" of an object and the speed of each, and I noticed that

Answer 1

All function calls have significant overhead -- you're creating a new stack frame to hold the new locals you have within your call, after all.

If this were a more expensive operation, that overhead would get lost in the noise. Since you're looking at such a trivial operation, it stands out.

Answer 2

(This is not supposed to be an answer, just documentation): These are the byte code sequences of the given expressions:

bool(a):

1           0 LOAD_NAME                0 (bool)
            3 LOAD_NAME                1 (a)
            6 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
            9 RETURN_VALUE

not a:

1           0 LOAD_NAME                0 (a)
            3 UNARY_NOT
            4 RETURN_VALUE

not not a:

1           0 LOAD_NAME                0 (a)
            3 UNARY_NOT
            4 UNARY_NOT
            5 RETURN_VALUE