You have been asked to write a username validation program for a small website. The website has specific rules on what constitutes a valid username, including: All usernames must be between 8 and 15 characters long Usernames can only contain alphabetic (a-z and A-Z) and numeric characters (0-9) - no special characters are allowed. The first character in a username cannot be a digit Usernames must contain at least one uppercase character Usernames must contain at least one lowercase character Usernames must contain at least one numeric character Write a program that asks the user to enter in a username and then examines that username to make sure it complies with the rules above. Here's a sample running of the program - note that you want to keep prompting the user until they supply you with a valid username:

Check the explanation

Explanation:

Python program to validate username and passwords and if invalid then fix the password to generate valid passwords

'''

import string

import random

# function to validate username

def username_validation(username):

              lowercase_letters = string.ascii_lowercase # string of all lowercase letters

              uppercase_letters = string.ascii_uppercase # string of all uppercase letters

              digits = string.digits

              num_uppercase = 0

              num_lowercase = 0

              num_digits = 0

              num_invalid = 0

              for letter in username:

                             if letter in lowercase_letters:

                                            num_lowercase = num_lowercase + 1

                             elif letter in uppercase_letters :

                                            num_uppercase = num_uppercase + 1

                             elif letter in         digits:

                                            num_digits = num_digits + 1

                             else:

                                            num_invalid = num_invalid + 1

              valid_start_end = not(username[0] in digits) and not(username[-1] in digits)

              print('* Length of username: %d'%(len(username)))

              print('* All characters are alpha-numeric: '),

              print(num_invalid == 0)

              print('* First & last characters are not digits: '+str(valid_start_end))

              print('* # of uppercase characters in the username: %d' %(num_uppercase))

              print('* # of lowercase characters in the username: %d' %(num_lowercase))

              print('* # of digits in the username: %d' %(num_digits))

              return(valid_start_end,num_uppercase,num_lowercase,num_digits,num_invalid)

# function to validate password  

def password_validation(username,password):

              while True:

                             (username_contained,num_lowercase,num_uppercase,num_special_chars,num_digits,num_invalid) = password_validation(username,password)

                             if(len(password) >= 8 and (not username_contained) and num_lowercase > 0 and num_uppercase > 0 and num_special_chars > 0 and num_invalid == 0):

                                            return password

                             if num_lowercase == 0:

                                            pos = random.randint(0,len(password)-1)

                                            letter = random.randint(0,len(lowercase_letters)-1)

                                            temp_password = password[0:pos] + lowercase_letters[letter]+ password[pos:]

                                            password = temp_password

                                            print('')

                                            print('* Adding a random lowercase character at a random position: '+password)

                             if num_uppercase == 0:

                                            pos = random.randint(0,len(password)-1)

                                            letter = random.randint(0,len(uppercase_letters)-1)

                                            temp_password = password[0:pos] + uppercase_letters[letter]+ password[pos:]

                                            password = temp_password

                                            print('* Adding a random uppercase character at a random position: '+password)

                             if num_special_chars == 0:

                                            pos = random.randint(0,len(password)-1)

                                            letter = random.randint(0,len(special_chars)-1)

                                            temp_password = password[0:pos] + special_chars[letter]+ password[pos:]

                                            password = temp_password

                                            print('* Adding a random special character at a random position: '+password)

                             if num_digits == 0:

                                            pos = random.randint(0,len(password)-1)

                                            letter = random.randint(0,len(digits)-1)

                                            temp_password = password[0:pos] + digits[letter]+ password[pos:]

                                            password = temp_password

                                            print('* Adding a random digit character at a random position: '+password)

                             if num_invalid > 0:

                                            i=0

                                            while i <len(password):

                                                           if password[i] not in valid_letters:

                                                                          temp_password = password[0:i] + password[i+1:]

                                                                          password = temp_password

                                                           else:

                                                                          i = i +1

                                            print('* Removing the invalid character from

                             (username_contained,num_lowercase,num_uppercase,num_special_chars,num_digits,num_invalid) = password_validation(username,password)

                             if(len(password) >= 8 and (not username_contained) and num_lowercase > 0 and num_uppercase > 0 and num_special_chars > 0 and num_invalid == 0 and num_digits > 0):

                                            break

                             else:

                                            print('* Length of password: %d' %(len(password)))

                                            print('* Username is part of password : '+str(username_contained))

                                            print('* # of uppercase characters in the password: %d' %(num_uppercase))

                                            print('* # of lowercase characters in the password: %d' %(num_lowercase))

                                            print('* # of digits in the password: %d' %(num_digits))

                                            print('* # of special characters in the password: %d'%(num_special_chars))

                                            print('* # of invalid characters in the password: %d' %(num_invalid))

                                            print('Password is invalid, please try again')

                                            choice = raw_input('\nWould you like us to fix your password for you? ')

                                            if choice.lower() == 'yes':

                                                           password = password_fixer(username,password)

                                                           print('Your new password is '+password)

                                            else:      

                                                           password = raw_input('\nEnter a password: ')

              print('Password is valid!')              

#call the main function  

if __name__ == "__main__":

              main()  

#end of program

###The full code is more than 5000 characters which is above character limit, so kindly check the below image for the complete code screenshot.