A Level Programming

Exceptional Handling

When the following program is run an error is generated

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n = "w"
n = int(n)
print(n)

With exceptional handling the program will run, fail gracefully but give the user information.

Copy the program into IDLE and run it entering a character ‘a’ and an integer ‘2’

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while True:
    try:
        n = input("Please enter an integer: ")
        n = int(n)
        break
    except ValueError:
        print("No valid integer! Please try again ...")
print("Great, you successfully entered an integer!")

The following program looks for a file that doesn’t exist. Rather than giving a messy red error message it gives information and fails gracefully. Try running it