Python Round() Function with Examples

It is a built-in function provided by python to round up any integer. If we pass a decimal number to the python round function with round off digits, it will return the floating number with rounded off value. If no digits are passed as a second parameter, it will round off the number nearest integer.

Syntax

round( input number, round off digits)

Parameters

1. Input number – number to be rounded off. (Required)
2. Round off digits – number of digits which input number is rounded off. (optional)

Examples of python round function

Passing an integer as a parameter to the python round function. It will return the same value.

Example 1

a = round(184)
b = round(957)
c = round(4397)

print(a)
print(b)
print(c)

Output

184
957
4397

Simple code of implementation round function with first parameter decimal and the second parameter is missing. Let’s see what its output is.

Example 2

a = round(5.4)
b = round(8.184)
c = round(9.34)

print(a)
print(b)
print(c)

Output

5
8
9

Passing negative integers as parameters to the round function.

Example 3

a = round(-10.5)
b = round(-54.34)
c = round(-37.2232)

print(a)
print(b)
print(c)

Output

-10
-54
-37

Python also provides ceil() function to round up the given number.

It takes the number and returns the number nearest integer that is greater than or equal to the given number. The ceil function is defined in the math library. So you should import the math library to use the ceil function in the program. Let’s see how it works.

Example

import math

a = math.ceil(2.5)
b = math.ceil(8.4)
c = math.ceil(9.1)

print(a)
print(b)
print(c)

Output:

3
9
10

Passing a negative integer to the ceil function will return a number nearest to the given number. An example of ceil function is given below.

Example

import math

a = math.ceil(-2.5)
b = math.ceil(-8.4)
c = math.ceil(-9.1)

print(a)
print(b)
print(c)

Output

-2
-8
-9

Exactly opposite working of ceil() python provides floor() function.

Python also provides a floor() function that works exactly the opposite of ceil function. The floor function returns an integer which is nearest that is less than or equal to the given number. It is defined in the math library. Let’s have a look at the working of the python floor function.

Example

import math

a = math.floor(2.5)
b = math.floor(8.4)
c = math.floor(6.8)

print(a)
print(b)
print(c)

Output

2
8
6

By passing a negative number as a parameter to it, it will return the nearest integer to the given number.

Example

import math

a = math.floor(-2.5)
b = math.floor(-8.4)
c = math.floor(-6.8)

print(a)
print(b)
print(c)

Output

-3
-9
-7

Using ceil and floor function we can make a user-defined function that will round up and round down the passed number as a parameter. 

Code of user-defined python round up function.

The first parameter is a number to be rounded off and the second parameter is the number of digits to be rounded off. The second parameter is set 0 as default so it is an optional parameter.

import math

def round_up(num, n=0):
   mult = 10 ** n
   return math.ceil(n * mult) / mult

1. Passing a number to the user-defined python round up function and second parameter is missing.

Example

a = round_up(146.54)
b = round_up(-242.5432)
c = round_up(4934.24)

print(a)
print(b)
print(c)

Output

147.0
-242.0
4935.0

2. Passing number as a first parameter and number of round off digits as a second parameter.

Example

a = round_up(146.54 ,1)
b = round_up(-242.543223 ,2)
c = round_up(4934.24233231, 3)

print(a)
print(b)
print(c)

Output

146.6
-242.54
4934.243

Code for user-defined python round down function.

import math

def round_up(num, n=0):
   mult = 10**n
   return math.floor(num * mult) / mult

1. Passing a number to the user-defined python round down function and second parameter is missing.

Example

a = round_up(49.495793)
b = round_up(-23784.53)
c = round_up(28.321)

print(a)
print(b)
print(c)

Output

49.0
-23785.0
28.0

2. Passing number as a first parameter and number of round off digits as a second parameter.

Example

a = round_up(49.495793 ,4)
b = round_up(-23784.53 ,2)
c = round_up(28.321,1)

print(a)
print(b)
print(c)

Output

49.4957
-23784.53
28.3

FAQ’s