Why are explicit calls to magic methods slower than “sugared” syntax?

Question

I was messing around with a small custom data object that needs to be hashable, comparable, and fast, when I ran into an odd-looking set of timing results. Some of the compa

Answer 1

Two reasons:

• The API lookups look at the type only. They don't look at self.foo.__hash__, they look for type(self.foo).__hash__. That's one less dictionary to look in.

• The C slot lookup is faster than the pure-Python attribute lookup (which will use __getattribute__); instead looking up the method objects (including the descriptor binding) is done entirely in C, bypassing __getattribute__.

So you'd have to cache the type(self._foo).__hash__ lookup locally, and even then the call would not be as fast as from C code. Just stick to the standard library functions if speed is at a premium.

Another reason to avoid calling the magic methods directly is that the comparison operators do more than just call one magic method; the methods have reflected versions too; for x < y, if x.__lt__ isn't defined or x.__lt__(y) returns the NotImplemented singleton, y.__gt__(x) is consulted as well.