A Beginner’s Guide to Decimal Points in Python

Skills for controlling decimal values

Handling decimal points is a critical skill in any programming language — especially when the focus is often data science.

Here’s a no-frills guide that covers the basics of rounding, truncating, and formatting decimal points in Python.

Rounding

Just like in elementary school, the first thing we’ll cover is rounding numbers.

To mimic the standard “five and up” rule, we’ll use the standalone round() function.

myNum = 3.14159265359
print(round(myNum,2) # 3.14
print(round(myNum,4) # 3.1416

What happens if you want to force rounding up or down? There are two methods of the pre-installed math library that can help you out.

To always round up, we’ll use the ceil() method — short for ceiling.

from math import ceil
myNum = 3.14159265359
print(ceil(myNum)) # 4

To always round down, we’ll use the floor() method — the opposite of a ceiling.

from math import floor
myNum = 3.14159265359
print(floor(myNum)) # 3