Python Program to Check Prime Number

Example 1: Using a flag variable

 # Program to check if a number is prime or not

num = 29

# To take input from the user

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

# define a flag variable

flag = False

# prime numbers are greater than 1

if num > 1:

    # check for factors

    for i in range(2, num):

        if (num % i) == 0:

            # if factor is found, set flag to True

            flag = True

            # break out of loop

            break

# check if flag is True

if flag:

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

else:

    print(num, "is a prime number")

Example 2: Using a for...else statement

# Program to check if a number is prime or not

num = 407

# To take input from the user

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

# prime numbers are greater than 1

if num > 1:

   # check for factors

   for i in range(2,num):

       if (num % i) == 0:

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

           print(i,"times",num//i,"is",num)

           break

   else:

       print(num,"is a prime number")

       

# if input number is less than

# or equal to 1, it is not prime

else:

   print(num,"is not a prime number")

Output

407 is not a prime number
11 times 37 is 407