I once was interested what exactly happens when executing python code, asking myself questions like "Why can't I make a fast for loop? Where are the fast integers? Can't I write fast for loop directly in bytecode, akin to asm?"<p>The python bytecode interpreter mainloop can be found in ceval.c.
There is a big switch case for each python bytecode opcode starting at <a href="https://github.com/python/cpython/blob/master/Python/ceval.c#L1480" rel="nofollow">https://github.com/python/cpython/blob/master/Python/ceval.c...</a><p>One can see even the simplest operations call quite a lot of stuff.
I gave up on fast pure cpython after reading ceval.c...