# How to Use the Python round() Function

09/10/2021

Contents

In this article, you will learn how to use the Python round() function.

## Python round() Function

The round() function in Python is used to round a number to a specified number of decimal places.

##### Syntax

Here is the syntax for using the round() function in Python:

``round(number, ndigits)``
##### Parameters
• `number`: The number to be rounded.
• `ndigits`: The number of decimal places to round the number to. If ndigits is not specified, the number is rounded to the nearest integer.
##### Example

Here are some examples of using the round() function in Python:

``````# rounding a float to the nearest integer
x = 3.14159
print(round(x)) # Output: 3

# rounding a float to 2 decimal places
x = 3.14159
print(round(x, 2)) # Output: 3.14

# rounding a float to 4 decimal places
x = 3.14159
print(round(x, 4)) # Output: 3.1416
``````

It’s important to note that the round() function follows the standard rounding rules. For example, if the first decimal place is 5 or greater, the number is rounded up; otherwise, it is rounded down.

Here are some additional things to keep in mind when using the round() function in Python:

• Rounding with ndigits=0 will always round to the nearest integer, regardless of the decimal value of the number. For example:

``````# rounding a float to the nearest integer (ndigits = 0)
x = 3.14159
print(round(x, 0)) # Output: 3
x = 3.7
print(round(x, 0)) # Output: 4
``````
• If ndigits is negative, the number is rounded to the left of the decimal point. For example:

``````# rounding a float to the nearest 10 (ndigits = -1)
x = 35.6
print(round(x, -1)) # Output: 40
x = 33.2
print(round(x, -1)) # Output: 30
``````
• The round() function returns a float if the input number is a float. If the input number is an integer, the round() function returns an integer.

``````# rounding an integer
x = 7
print(round(x)) # Output: 7 (int)

# rounding a float
x = 7.0
print(round(x)) # Output: 7 (float)
``````
• If the input number is not a valid number (e.g., None, float(‘inf’), etc.), a TypeError will be raised.