rounding - Round to 5 (or other number) in Python

Question

Is there a built-in function that can round like the following?

10 -> 10
12 -> 10
13 -> 15
14 -> 15
16 -> 15
18 -> 20

Answer 1

I don't know of a standard function in Python, but this works for me:

Python 3

def myround(x, base=5):
    return base * round(x/base)

It is easy to see why the above works. You want to make sure that your number divided by 5 is an integer, correctly rounded. So, we first do exactly that (round(x/5)), and then since we divided by 5, we multiply by 5 as well.

I made the function more generic by giving it a base parameter, defaulting to 5.

Python 2

In Python 2, float(x) would be needed to ensure that / does floating-point division, and a final conversion to int is needed because round() returns a floating-point value in Python 2.

def myround(x, base=5):
    return int(base * round(float(x)/base))