Input Validation
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Input validation is important to prevent incorrect or invalid values from being entered into an application which could lead to user frustration or security issues. Exceptions handle errors and unexpected conditions during program execution. Common exceptions include ImportError, ValueError, and IOError. The try-except block allows code to be executed within the try statement and exceptions raised to be handled in the except block through predefined or custom exceptions.
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Input Validation
- 2. WHY VALIDATE INPUT Validating user input is fundamental in application development. It prevents users/systems from inadvertently entering incorrect values or values that should not be allowed into the application. Incorrect input can lead to user frustration or serious security concerns
- 3. EXCEPTIONS An exception is a signal that a specific condition has occurred that can’t be easily handled by normal program flow. Ex. Trying to perform a calculation on a string Typically your application will error and crash, however with exception handling we can catch the error and safely exit the application, fix the issue, or try again. Exceptions are preprogrammed conditional statements for error catching, however you can create your own error messages.
- 4. COMMON EXCEPTIONS ImportError – module not found ValueError – Inappropriate value KeyboardInterupt – When user terminates application IOError – file cannot be opened
- 5. TRY-EXCEPT Code: try: statement 1 to attempt statement 2 to attempt . . . except: OPTIONAL EXCEPTION USER CREATED EXCEPTION
- 6. TRY-CATCH EXAMPLE try: val = int(input(“Enter a number”) except: ValueError try: val = int(input(“Enter a number”) except: ValueError print(“Not a valid number”) try: val = int(input(“Enter a number”) except: MyException print(“Not a valid number”) quit