Is there a ceiling equivalent of // operator in Python?

Question

I found out about the // operator in Python which in Python 3 does division with floor.

Is there an operator which divides with ceil instead? (I know about the / operator which in Python 3 does floating point division.)

Answer 1

You can just do upside-down floor division:

def ceildiv(a, b):
    return -(-a // b)

This works because Python's division operator does floor division (unlike in C, where integer division truncates the fractional part).

This also works with Python's big integers, because there's no (lossy) floating-point conversion.

Here's a demonstration:

>>> from __future__ import division   # a/b is float division
>>> from math import ceil
>>> b = 3
>>> for a in range(-7, 8):
...     print(["%d/%d" % (a, b), int(ceil(a / b)), -(-a // b)])
... 
['-7/3', -2, -2]
['-6/3', -2, -2]
['-5/3', -1, -1]
['-4/3', -1, -1]
['-3/3', -1, -1]
['-2/3', 0, 0]
['-1/3', 0, 0]
['0/3', 0, 0]
['1/3', 1, 1]
['2/3', 1, 1]
['3/3', 1, 1]
['4/3', 2, 2]
['5/3', 2, 2]
['6/3', 2, 2]
['7/3', 3, 3]