How can you tell if a number is odd or even in Python?

The easiest way to determine if a number is even or odd in Python is to use the modulus operator. This operator, denoted as the percentage sign % displays the remainder from a division operation. To determine if a number is even simply apply my_number % 2 == 0 where my_number is your number and if this result is True then your number is even, otherwise, it is odd.

Here’s a simple example demonstrating how this works:

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>>> im_even = 6
>>> im_even % 2 == 0
True
>>> im_odd = 5
>>> im_odd % 2 == 0
False

isodd & iseven Functions

From this understanding you can even create your own isodd or iseven function depending on how often you need to perform this comparison in your code.

An example of your own isodd or iseven function could look something like this:

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def iseven(n):
    return n % 2 == 0

def isodd(n):
    return n % 2 == 1

As you can see from the two functions above there is a slight difference in each where if the result of the modulo operation produces a zero for the iseven function then you know the number is even, whereas for the isodd function compares the modulo result to 1.

Both results from the functions would return True if the number inserted into the parameter satisfies the conditions.

Here is an example of the output when applying these functions:

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>>> iseven(6)
True
>>> isodd(5)
True
>>> iseven(7)
False
>>> isodd(8)
False

As you can see the operation is a little tidier and should make clear sense to anybody reading your code.

Summary

The modulus operator is another arithmetic operator available in Python and can help in determining whether a number is odd or even. Using the modulus operator with the number 2 will help to show if there is a remainder or not with any number.

The result from the operation my_number % 2 will either produce a 0 or 1, with 0 implying the number is even – as all even numbers can be divided by 2, and 1 implying the number is odd.

You can also wrap this modulo operation into your own custom functions isodd and iseven by extending it with a comparison to 0 or 1. This might help make your code more easy to read.