Create An Email Validation Using Regular Expression in The Python Assignment Solution.

TASK 1

def factorial(n):

    # starting with value 1

    result = 1

    # keep multiplying by consecutive integers including n

    for i in range(n):

        result *= (i + 1)

    return result

def main():

    # keep asking user until nonnegative value is entered

    while True:

        n = int(input('Please input a nonnegative integer? '))

        if n >= 0:

            # calculating factorial of given integer

            print('Factorial of', n, ':', factorial(n))

            return

        else:

            # showing error message

            print('Please enter a nonnegative integer')

            print()

if __name__ == '__main__':

    main()

TASK 2

def factorial(n):

    # if n == 0, returning 1

    if n == 0:

        return 1

    # returning result as a product of (n-1)! and n

    return factorial(n-1) * n

def main():

    # keep asking user until nonnegative value is entered

    while True:

        n = int(input('Please input a nonnegative integer? '))

        if n >= 0:

            # calculating factorial of given integer

            print('Factorial of', n, ':', factorial(n))

            return

        else:

            # showing error message

            print('Please enter a nonnegative integer')

            print()

if __name__ == '__main__':

    main()

TASK 3

import re

def check_email(email):

    # using following regex:

    # - positive number of symbols: alphanumeric/-/.

    # - single @

    # - positive number of symbols: alphanumeric/-/.

    regex = '^[\w\-.]+[@][\w\-.]+$'

    if re.search(regex, email):

        # if email matches pattern, searching for index of '@'

        idx = email.index('@')

        # returning separated username and host, as a tuple

        return email[:idx], email[idx+1:]

    # if valid is not valid, returning None

    return None

def main():

    # keep asking user until value email is entered

    while True:

        result = check_email(input('Please input your email address:').strip())

        if result:

            # outputting result of email parsing

            print('email: ', result[0] + '@' + result[1], ',', 'username: ', result[0], ',', 'host: ', result[1])

            return

        else:

            # showing error message

            print('Not a valid email.')

            print()

if __name__ == '__main__':

    main()