Python Program to check a number is prime or not

In this simple python program, we need to check the given number is prime or not. It's a beginner-level python program.

To understand this example, you should have knowledge of the following Python programming topics:

What is the prime number?

In this python program, we need to check for a Prime number. A Prime number is a positive number that is divisible by 1 and by that number only. So for a prime number, there will be only two factors.

For example, let us take a number 7, so let's check the 7 is a positive number and divisible by 7 and 1 only, so it is a prime number.

How to check a number is prime or not in the python program?

Note: 1 is not a prime number because 1 has only one factor, so we treat it as 1 is not a prime number.

In this simple python program, we need to accept a number from the user and save that into a variable. Now we check the number for prime or not by checking the number is positive or not. If it is not a positive number, we cant check for the prime. We have to use a for loop in python from 2 to the number and check that number is divisible by any number below that number using an if condition in python language. Finally, print the number is prime or not.

ALGORITHM

STEP 1: Accept the number from the user using the input function in python and store it in a variable.

STEP 2: check the number is greater than 1. If so, move inside the if condition else print the number is not prime because it is not a positive number.

STEP 3: Open a for loop from 2 to the entered number to check for the number's divisibility.

STEP 4: Open an inner if condition to mod the number with every number from 2 to that number. Print the given number is not a prime number is divisible with any number, and break the loop using the break statement.

STEP 5: If that loop is over and no number is found divisible with the given number, print the given number as a prime number.

Python Source Code

                                          num = int(input("Enter any number: "))  # Accept the number from the user.

if num > 1:   # check the number is greater than 1.

    for i in range(2, num):         # for loop to check the number is divisible by any number

        if (num % i) == 0:      # If condition to check any divisor for the number

            print(num, "it is not a prime number")

            break     # break from the for loop

    else:

        print(num, "it is a prime number")    # if the number is less than or equal to zero then it is not a prime number
else:

    print(num, "it is not a prime number")
                                      

OUTPUT

Enter any number:  7

7 It is a prime number