How to do division rounding in Python?

In Python, you can perform division rounding using a few different methods, primarily focusing on floor division for rounding down, and standard division with rounding functions for other behaviors.

Floor Division (Rounding Down)

The most direct way to perform division that results in rounding down to the nearest whole number is to use the floor division operator //. This operator is also known as integer division.

result = 10 // 3
print(result)  # Output: 3

result = -10 // 3
print(result)  # Output: -4 (rounds towards negative infinity)

As shown in the examples, floor division rounds the result down to the nearest integer, even when dealing with negative numbers.

Rounding with round() function

Python's built-in round() function can be used for general rounding to the nearest integer or to a specified number of decimal places.

result = round(10 / 3)  # Rounds to nearest integer
print(result)  # Output: 3

result = round(10 / 3, 2) # Rounds to 2 decimal places
print(result)  # Output: 3.33

Keep in mind that round() uses banker's rounding (rounding to the nearest even number) in Python 3 for halfway cases.

Rounding Up with math.ceil()

If you need to always round up to the nearest integer, you can use the math.ceil() function.

import math

result = math.ceil(10 / 3)
print(result)  # Output: 4

result = math.ceil(-10 / 3)
print(result)  # Output: -3

Rounding Down with math.floor()

While // is the most common way to perform floor division, you can also use math.floor().

import math

result = math.floor(10 / 3)
print(result) # Output: 3

result = math.floor(-10 / 3)
print(result) # Output: -4

In summary, Python provides several options for division rounding, catering to different needs such as rounding down, rounding up, or rounding to the nearest integer or decimal place. Use // for floor division, math.ceil() for rounding up, math.floor() as an alternative to // for floor division, and round() for general-purpose rounding.