An odd number is a number you cannot divide into two equal parts. An even number is a number you can evenly divide into two parts. In Python, you can use the modulo operator (%) to check if a number is odd or even.
For example:
n = 9 # 1. Check if a number is odd is_odd = n % 2 != 0 # 2. Check if a number is even is_even = n % 2 == 0
This guide teaches you how to check if a number is odd or even and how the modulo operator works in Python.
The Modulo Operator in Python
In Python, the modulo operator (%) returns the remainder in the division between two numbers.
Here’s how you can use it:
a % b
If this operation returns 0, it means a is evenly divisible by b.
For example, if you have 15 slices of pizza for 3 guests and you want to check if you can share the 15 slices with your guests evenly, you can use the modulo operator:
print(15 % 3)
Output:
0
Make sure to check my complete guide to modulos in Python.
How to Use Modulo to Figure Out If a Number Is Odd or Even?
The modulo operator returns the remainder in the division.
By definition:
- An odd number isn’t evenly divisible by 2.
- An even number is evenly divisible by 2.
In the context of modulos, this means:
- Calculating modulo between an odd number and 2 returns 1 as a leftover value.
- Calculating modulo between an even number and 2 returns 0.
How to Check If a Number Is Even in Python?
You can use the modulo operator in Python to check if a number is even.
If you take a modulo between an even number and 2, the result is 0.
To write a program that checks if a number is even:
- Take the modulo between your target number and 2.
- Use a comparison operator to check if the result is equal to 0.
For example, let’s check if the number 9 is even:
number = 9 is_even = number % 2 == 0 print(is_even)
Output:
False
How to Check If a Number is Odd in Python
You can also use the modulo operator in Python to check if a number is odd.
If you take a modulo between an odd number and 2, the result is 1.
To write a program that checks if a number is odd:
- Take the modulo between your target number and 2.
- Use a comparison operator to check if the result is 1.
For instance, let’s see if the number 11 is odd:
number = 11 is_odd = number % 2 == 1 print(is_odd)
Output:
True
Example 1. Write a Function That Checks If a Number Is Odd/Even
In the previous examples, you learned how to use the modulo operator to check if a value is odd or even in Python.
But the above examples are just standalone code expressions. If you want to reuse the odd/even logic, you’d have to rewrite the comparisons over and over again.
To improve your code quality and readability, you can implement functions for checking if an input number is odd/even. This way you can reuse the code by calling the name of the function.
Here are two functions for calculating if a value is odd or even:
def is_even(n):
return n % 2 == 0
def is_odd(n):
return n % 2 != 0
Now you can use these functions anywhere and any number of times in your code.
For example:
print(is_odd(10)) print(is_even(6))
Output:
False True
Example 2. Check If User Input Is Odd/Even
A common beginner-friendly Python example is to take user input and check if the input is odd/even.
Here’s a program that does it for you:
number = int(input("Enter a number: "))
if number % 2 == 0:
print("The number is even")
else:
print("The number is odd")
Example output:
Enter a number: 16 The number is even
Here:
- The input() function takes the user input in the console.
- The int() call converts the input to an integer from a string (text).
- The if-else statement checks if the input number is divisible by 2 or not.
Summary
Today you learned how to use Python to check if a number is odd or even.
To take home, you can use the modulo operator (%) to check for odd/even values. If the % operator returns 0 between a number and 2, the value is evenly divisible by 2 and is thus even. If the result is 1, the number is not divisible by 2, which means it’s odd.
Thanks for reading. Happy coding!