Python round() Function: Usage and Examples

This guide explains round() Function: Usage and Examples through a focused example and practical reasoning. No prior knowledge of this specific operation is required.

Understanding the Concept

round(number, digits) rounds a number for display or further numeric use. When a result is exactly halfway between two choices, Python uses round-to-even for exact ties; binary floating-point often makes apparent decimal ties inexact.

When You Would Use This

Round a collection of measurements but distinguish the stored reading from the rounded display.

Step-by-Step Example

print(round(2.5))
print(round(3.5))
print(round(12.345, 2))
print(f"{12.345:.2f}")

How the Example Works

The first two calls return 2 and 4 because ties go to even numbers. Values like 12.345 are not necessarily represented exactly as binary floats, so decimal-looking half ties can surprise you.

Example Output

Try It Yourself

Check round(-2.5) and compare it with round(-3.5).

Common Beginner Mistakes

Assuming half values always round away from zero.
Rounding each line item prematurely before summing financial totals.
Expecting round() to fix binary floating-point approximation.

Key Takeaways

round(number, digits) rounds a number for display or further numeric use.
The first two calls return 2 and 4 because ties go to even numbers.
Avoid this mistake: Assuming half values always round away from zero.