17.8. Exercises: Local Development

Take a moment to think about how many logins you use each day. Do you have different passwords for each one? How many characters do they contain? Do you mix letters, digits, and special characters? Do you use the same password multiple times, even though that’s a bad idea?

There are lots of password manager applications on the market these days. One feature of these apps lets users quickly create new, strong passwords.

The logic behind a password generator is fairly straightforward. In these exercises, you will use your Python skills to make one!

17.8.1. Setup

  1. Open Visual Studio Code and create a new directory. Also, create an empty .py file for your program. Be sure to follow the proper Python naming conventions.

  2. In your new file, start by adding import statements for the random and string modules.

  3. This program might be used as a module later, so you need to set up your main() function as described in the More About main() section.

    def main():
   print('Welcome to the password generator!')
   # Your code here...

if __name__ == "__main__":
   main()

17.8.2. Part A: Choose a Length

Write a function called pw_length that does the following:

  1. Prompts the user to choose a length for their new password. Acceptable values range from 8 - 30 characters.

  2. Uses a while loop to validate the user’s entry. If an entry is invalid, the loop should print an error message and reprompt the user for the length.

  3. Returns an integer for the password length.

Note

Be sure to test your function! In main() call pw_length and print the value returned by the function.

Try entering invalid options like abc, 33, -2, and 3.14159. Also, check to make sure the edge values 8 and 30 both work.

Sample Output

Welcome to the password generator!
Choose a password length (8 - 30 characters): 2
Please enter a whole number from 8 - 30.
Choose a password length (8 - 30 characters): Hello
Please enter a whole number from 8 - 30.
Choose a password length (8 - 30 characters): 10
Returned value = 10

17.8.3. Part B: Include Special Characters?

Write a boolean function called includes_special() that does the following:

  1. Asks if the user wants to include special characters in the new password. Special characters include symbols like &, }, *, etc.

  2. Uses a while loop to accept only yes/no or Y/N answers. These options should be case-insensitive.

  3. Returns the boolean True or False based on the user’s choice.

In main() call and test includes_special().

Sample Output

Welcome to the password generator!
Include special characters (Y/N)? no
Please enter 'Y' or 'N'.
Include special characters (Y/N)? 0
Please enter 'Y' or 'N'.
Include special characters (Y/N)? y
Returned value = True

17.8.4. Part C: Generate New Password

Write a function called make_password() that does the following:

  1. Calls the pw_length and includes_special functions.

  2. Defines a characters variable that:

    1. Combines string.ascii_letters and string.digits (to get all upper and lowercase letters, plus the digits 0-9).

    2. Includes string.punctuation if the user wants special characters.

  3. Builds a new password by randomly choosing from the characters string.

  4. Returns the new password.

In main() remove (or comment out) any function calls and print statements you used to test Parts A and B.

Call make_password() and assign the returned value to a variable. Print out the password to check your work. Repeat your test several times, both with and without special characters.

Sample Output

Welcome to the password generator!
Choose a password length (8 - 30 characters): 15
Include special characters (Y/N)? y
Your new password is: Sd"A%OO0nSzU?52

17.8.5. Part D: Add a Login Class

Below the import statements, define a Login class.

  1. Use the __init__ method to initialize properties for a site name, a username, and a password.

  2. Define a method called change_password that calls the make_password function and updates the password property.

  3. Define a __str__ method that displays the login information in a clean way.

Test your class by creating a new Login object (you will need to prompt for the site and username).

Be sure to print the object to the console before and after calling the change_password method.

Warning

It NOT a good idea to print passwords to the screen or save them without encrypting them! You are just doing it here to test your code.

Sample Output

Welcome to the password generator!
Please enter the site name: WOPR
Please create a username: imsai8080
Choose a password length (8 - 30 characters): 8
Include special characters (Y/N)? n

Login for: WOPR
Username: imsai8080
Password: 0cFqu5hc

Would you like to change your password (Y/N)? y
Choose a password length (8 - 30 characters): 30
Include special characters (Y/N)? y
imsai8080, your new WOPR password is: &,|]ws@Rlb[)Rj&^5BOg)(]m&|Aj__

17.8.6. Part E: Final Touch (Optional)

If a user doesn’t like the password generated, they must rerun the program and enter their choices for the length and special characters again. Some people will find this annoying.

Modify your make_password function to give the user a preview of their new password. If they don’t like it, have the function generate new ones until the user accepts. These follow-up options should not require the user to enter a length or special character choice.