Page 222 - Beginning Programming with Pyth - John Paul Mueller

TryAgain = False
except KeyboardInterrupt:
print("You pressed Ctrl+C!")
print("See you next time!")
TryAgain = False
else:
print(Value)
TryAgain = False
The code begins by creating an input loop. Using loops for this type of purpose is actually quite common in applications because you don’t want the application to end every time an input error is made. This is a simplified loop, and normally you create a separate function to hold the code.
When the loop starts, the application asks the user to type a whole number. It can be any integer value. If the user types any non- integer value or presses Ctrl+C, Cmd+C, or another interrupt key combination, the exception-handling code takes over. Otherwise, the application prints the value that the user supplied and sets TryAgain to False, which causes the loop to end.
A ValueError exception can occur when the user makes a mistake. Because you don’t know why the user input the wrong value, you have to ask if the user wants to try again. Of course, getting more input from the user could generate another exception. The inner try...except code block handles this secondary input.
Notice the use of the str.upper() function when getting character input from the user. This function makes it possible to receive y or Y as input and accept them both. Whenever you ask the user for character input, converting lowercase characters to uppercase is a good idea so that you can perform a single comparison (reducing the potential for error).
The KeyboardInterrupt exception displays two messages and then exits automatically by setting TryAgain to False. The KeyboardInterrupt occurs only when the user presses a specific key combination designed to end the application. The user is