Python Float to Int

Summary: in this tutorial, you’ll learn how to convert a float to an integer.

Suppose that you have a float such as 20.3, and you want to convert it to an integer.

When you convert a float to an integer, you’ll have a data loss. For example, 20.3 may become 20 or 21.

Python provides you with some functions in the math module for converting from a float to an int, including:

• Truncation
• Floor
• ceiling

Truncation #

The trunc(x) function returns the integer part of the number x. It ignores everything after the decimal point. For example:

from math import trunc

print(trunc(12.2))
print(trunc(12.5))
print(trunc(12.7))Code language: Python (python)

Output:

12
12
12Code language: Python (python)

Similarly, the int() constructor accepts a float and uses truncation to cast a float to an int:

print(int(12.2))
print(int(12.5))
print(int(12.7))Code language: Python (python)

Floor #

The floor(x) function returns the largest integer less than or equal to x. For example:

from math import floor

print(floor(12.2))
print(floor(12.5))
print(floor(12.7))Code language: Python (python)

Output:

12
12
12Code language: Python (python)

The following shows how floor() function is applied to a positive number:

[]

For positive numbers, floor(x) and trunc(x) return the same result. However, it’s not the case for negative numbers. For example:

[]

The following picture shows how the floor() function is applied to a negative number:

from math import floor, trunc

print(floor(-12.7))
print(trunc(-12.7))Code language: Python (python)

Output:

-13
-12Code language: Python (python)

The following picture illustrates the difference between the floor() and trunc() function when you apply them to a negative number:

[Python float to int - floor vs trunc]

Ceiling #

The ceil(x) function returns the smallest integer greater than or equal to x. For example:

from math import ceil


print(ceil(12.7))Code language: Python (python)

Output:

13Code language: Python (python)

The following illustrates how the ceil() function is applied to a positive number:

[]

This example uses the ceil() function for negative numbers:

from math import ceil

print(ceil(-12.7))
Code language: JavaScript (javascript)

Output:

-12

The following illustrates how the ceil() function is applied to a negative number:

[]

Summary #

• Convert a float to an int always results in a data loss.
• The trunc() function returns the integer part of a number.
• The floor() function returns the largest integer less than or equal to a number.
• The ceil() function returns the smallest integer greater than or equal to a number.