`round()` Function in Python [ English ]

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1. Introduction

The round() function in Python is a built-in function used to round a number to a specified number of digits. It returns the number rounded to the nearest integer or to a specified number of decimal places.

The round() function is commonly used in programs where approximate values or formatted numbers are required, such as financial calculations, measurements, and statistical results.

2. Syntax

round(number, ndigits)

Parameters

1. number The numeric value that needs to be rounded.

2. ndigits (optional) The number of decimal places to which the number should be rounded.

   • If not specified, the number is rounded to the nearest integer.

3. Return Value

• Returns the rounded value of the given number.

4. Example: Rounding to Nearest Integer

print(round(4.6))
print(round(4.2))

Output

5
4

Explanation

• 4.6 is rounded up to 5.
• 4.2 is rounded down to 4.

5. Example with Decimal Places

print(round(3.14159, 2))

Output

3.14

Explanation

• The number is rounded to 2 decimal places.

6. Example with One Decimal Place

print(round(7.856, 1))

Output

7.9

Explanation

• The value is rounded to one decimal place.

7. Example with Negative ndigits

Negative values for ndigits round numbers to tens, hundreds, etc.

print(round(125, -1))
print(round(125, -2))

Output

120
100

Explanation

• -1 rounds the number to the nearest ten.
• -2 rounds the number to the nearest hundred.

8. Example Showing Special Rounding Behavior

print(round(2.5))
print(round(3.5))

Output

2
4

Explanation

Python uses "round half to even" (also called banker's rounding):

• 2.5 → rounded to 2 (nearest even number)
• 3.5 → rounded to 4 (nearest even number)

9. Practical Example

price = 123.4567

rounded_price = round(price, 2)

print("Rounded Price:", rounded_price)

Output

Rounded Price: 123.46

Explanation

• The price is rounded to two decimal places, which is common in financial calculations.

10. Summary

• round() is a built-in Python function used to round numbers.
• It can round numbers to the nearest integer or to a specified number of decimal places.
• The optional ndigits parameter controls the number of decimal digits.
• Negative values of ndigits round numbers to tens, hundreds, etc.
• Python uses round half to even when the value ends with .5.