Program to Check if a Number is Prime in Python

Checking Prime Number

A prime number is a natural number greater than 1 that has no divisors other than 1 and itself.

We will explore different methods to check if a number is prime using Python programming.

Method 1: Using a for Loop

We iterate from 2 to the square root of the number and check for divisibility.

num = int(input("Enter a number: "))
is_prime = True

if num < 2:
    is_prime = False
else:
    for i in range(2, int(num ** 0.5) + 1):
        if num % i == 0:
            is_prime = False
            break

if is_prime:
    print(f"{num} is a prime number")
else:
    print(f"{num} is not a prime number")
            

Output:

Enter a number: 7
7 is a prime number

Method 2: Using a Function

We create a function to check for primality and return the result.

def is_prime(num):
    if num < 2:
        return False
    for i in range(2, int(num ** 0.5) + 1):
        if num % i == 0:
            return False
    return True

num = int(input("Enter a number: "))

if is_prime(num):
    print(f"{num} is a prime number")
else:
    print(f"{num} is not a prime number")
            

Output:

Enter a number: 10
10 is not a prime number