The round() function rounds a number to a specified number of decimal places. It’s useful for financial calculations, data formatting, and improving numerical readability.
Example
print(round(3.14159, 2))Output:
3.14Rounds 3.14159 to 2 decimal places.
Syntax
round(number, ndigits=None)- number → The number to round.
- ndigits (optional) → Number of decimal places to keep (
default: 0). - Returns → A rounded integer or floating-point number.
1. Rounding to the Nearest Integer
print(round(4.6)) # Output: 5
print(round(4.3)) # Output: 4If ndigits is not specified, it rounds to the nearest integer.
2. Rounding to a Specific Decimal Place
print(round(3.14159, 3)) # Output: 3.142
print(round(9.8765, 1)) # Output: 9.9Keeps a specific number of decimal places.
3. Rounding Negative Numbers
print(round(-2.8)) # Output: -3
print(round(-2.4)) # Output: -2Negative numbers round away from zero or towards zero, depending on .5 rules.
4. Rounding to the Nearest Multiple of 10
print(round(1234, -2)) # Output: 1200Useful for rounding large numbers.
5. Handling .5 Rounding Behavior (Bankers’ Rounding)
Python follows “bankers’ rounding” (ties round to the nearest even number).
print(round(2.5)) # Output: 2
print(round(3.5)) # Output: 4- 2.5 rounds to 2 (even).
- 3.5 rounds to 4 (even).
6. Using round() in Division Calculations
average = round(10 / 3, 2)
print(average) # Output: 3.33Keeps precision in floating-point division.
Key Notes
- ✔ Rounds numbers to the nearest integer or decimal place.
- ✔ Uses “bankers’ rounding” (ties round to the nearest even number).
- ✔ Useful for formatting financial data and scientific calculations.
- ✔ Handles both positive and negative numbers.
By using round(), you can format numbers neatly, ensure accuracy in calculations, and control decimal precision efficiently. 🚀