Truncating division in Python 3.2

Question

1. Is integer floor division // faster than float division / in Python 3.2? If I know I'm going to be working with integers only, should I favour // instead of defaulting to /?

2. How do I get integer truncation behaviour in Python 3.2?

   1/2 = 0

   -1/2 = 0

Thanks.

Answer 1

from math import (floor, ceil)
def trunc_div(a, b):
    c = a / b
    return floor(c) if c > 0 else ceil(c)

Test it to make sure it's right. It's late and I'm doing math while sleepy.

Actually, don't do that. While seeing if I could subclass int to do truncated division (don't do that either (also, it didn't work)), it occurred to me that int() itself will truncate reals, resulting in this:

def trunc_div(a, b):
    return int(a / b)

Which is a rather foolish wrapper.

So, just use float division, and truncate it with int():

>>> int(1 / 2)
0
>>> int(-1 / 2)
0

This gets you pretty close to the infix notation you desired.

The moral of this story is... don't let your friends code while drowsy.