Day 8 : Python Program to check whether the number is prime or not using recursion

def is_prime(number, divisor=2):

    if number <= 1:

        return False

    if divisor == number:  

        return True

    if number % divisor == 0:  

        return False

    return is_prime(number, divisor + 1) 

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.")

Code Explanation

Function Definition

def is_prime(number, divisor=2):

number: The number to check for primality.

divisor=2: The starting divisor for checking divisibility. Defaults to 2.

Base Cases

Check if the number is 

if number <= 1:

    return False

Numbers less than or equal to 1 are not prime.

Returns False.

Check if the divisor has reached the number:

if divisor == number:

    return True

If the divisor equals the number, it means no smaller divisors were found, so the number is prime.

Returns True.

Recursive Check

python

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if number % divisor == 0:

    return False

If number % divisor == 0, it means the number is divisible by divisor, so it's not a prime number.

Returns False.

return is_prime(number, divisor + 1)

If no divisors are found, the function recursively calls itself, increasing the divisor by 1 to check the next potential divisor.

Input

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

Prompts the user to input a number.

int() ensures the input is treated as an integer.

Prime Check and Output

if is_prime(num):

    print(f"{num} is a prime number.")

else:

    print(f"{num} is not a prime number.")

Calls the is_prime function with the input number.

Depending on the result (True or False), it prints whether the number is prime.

#source code --> clcoding.com