Why does Python code run faster in a function?

Question

def main():  for i in xrange(10**8):   pass main()This piece of code in Python runs in (Note: The timing is done with the time function in BASH in Linux.) real 0m1.841s user 0m1.828s sys  0m0.012sHowever, if the for loop isn't placed within a function, for i in xrange(10**8):  passthen it runs for a much longer time: real 0m4.543s user 0m4.524s sys  0m0.012sWhy is this?

Answer 1

 Some experts says that it's a problem of local/global variable store times

But it can be because of opcode prediction makes the function faster.

As the other answers explain, the function uses the STORE_FAST opcode in the loop. Here's the bytecode for the function's loop:

>> 13 FOR_ITER 6 (to 22) # get next value from iterator16 STORE_FAST 0 (x) # set local variable19 JUMP_ABSOLUTE 13 # back to FOR_ITER