Intro

For the last few lessons we have been looking at pseudocode and WHILE loops.

One of the classic uses for WHILE loops is to validate text entry in web forms.  For example, a form may require that usernames must be in all lowercase.  

Python has a handy function that returns true if the string is in lowercase. Consider the following example :

lower_string = "hello"
upper_string = "Hello"
mixed_string = "Hello"
print(lower_string.islower() )
print(upper_string.islower() )
print(mixed_string.islower() )

If you were to run this program in IDLE or Trinket, to output would be:
True
False
False
This is because:
  • It is true that the variable lower_string is made up of all lowercase characters.
  • It is not true that the variable upper_string is made up of all lowercase characters.
  • Similarly, is not true that the variable mixed_string is made up of all lowercase characters (it is a mixture of lower and uppercase characters).
The following video demonstrates this (and other related) function/s.
Video - lower(), upper(), islower(), isupper() Python functions

                    

                    
Must
Write a program that:
  1. Asks the user to input their username.
  2. Stores the input into a variable call username.
  3. Uses a WHILE statement to check if the username is not all lowercase.
  4. Inside the WHILE block (under the WHILE statement), repeats instructions 1 and 2.
Submit work as a screen shot from Trinket/IDLE, showing your code and the program having run.
Could
  • Extend the WHILE condition to check if the users name is all lowercase AND is at least 8 characters long.  Use the len() function to count how many characters are in a string.
This video will help:

                    

                    

Submit work as a screen shot from Trinket/IDLE, showing your code and the program having run.