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

## Instructions

Objective
Write a python assignment program to create an email validation using regular expression.

## Requirements and Specifications

Screenshot

Source Code

```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()```