How to Get the Integer Part of a Decimal Number in Python?

Find out how to get the digits before a decimal point in Python

In Python, you can get the integer part of a decimal number in the following ways:

Using int()

You can use the int() method to truncate floating point numbers towards zero, discarding the fractional component of a number and returning only the integer part.

For example:

print(int(10 / 3)) # 3
print(int(-10 / 3)) # -3
print(int(10 / -3)) # -3

print(int(3.333)) # 3
print(int(-3.333)) # -3
print(int(5 / 2)) # 2
print(int(-5 / 2)) # -2
print(int(5 / -2)) # -2

print(int(2.5)) # 2
print(int(-2.5)) # -2
print(int(10 / 1)) # 10
print(int(-10 / 1)) # -10
print(int(10 / -1)) # -10

print(int(10.0)) # 10
print(int(-10.5)) # -10

Using math.floor() and math.ceil()

To achieve the same effect as with int(), you can:

  • Use math.floor() to round down positive integers, and;
  • Use math.ceil() to round up negative integers.

Doing so would truncate a floating point number towards zero. You can implement it, for example, like so:

import math

def trunc(num):
    return math.floor(num) if (num > 0) else math.ceil(num)

You can also implement this using only the math.floor() method like so:

import math

def trunc(num):
    unsigned_num = math.floor(abs(num))
    return -unsigned_num if (num < 0) else unsigned_num

Similarly, you can implement this using only the math.ceil() method like so:

import math

def trunc(num):
    unsigned_num = math.ceil(-abs(num))
    return unsigned_num if (num < 0) else -unsigned_num

Using any of these would yield the same result (as you can see in the examples below):

print(trunc(10 / 3)) # 3
print(trunc(-10 / 3)) # -3
print(trunc(10 / -3)) # -3

print(trunc(3.333)) # 3
print(trunc(-3.333)) # -3
print(trunc(5 / 2)) # 2
print(trunc(-5 / 2)) # -2
print(trunc(5 / -2)) # -2

print(trunc(2.5)) # 2
print(trunc(-2.5)) # -2
print(trunc(10 / 1)) # 10
print(trunc(-10 / 1)) # -10
print(trunc(10 / -1)) # -10

print(trunc(10.0)) # 10
print(trunc(-10.5)) # -10

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