CSC111 Lab 9 2015

--D. Thiebaut (talk) 07:14, 29 March 2015 (EDT)

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Exceptions

preparation

• Create a new program called lab9_1.py, and copy this code to the new Idle window.

# getInput: returns an integer larger
# than 0.  Expected to be robust
def getInput():
   x = int( input( "Enter an integer larger than 0:  " ) )
   while  x <= 0:
        x = int( input( "Invalid number: Please try again: " ) )
   return x

def main():
   num = getInput()
   print( "You have entered", num )

main()

• Test it with numbers such as -3, -10, 0, 5. Verify that the input function works well when you enter numbers.
• Test your program again, and this time enter expressions such as "6.3", or "hello" (without the quotes).
• Make a note of the Error reported by Python:

• Modify your function and add code that will catch the exception:

# getInput: returns an integer larger
# than 0.  Expected to be robust
def getInput():
   x = int( input( "Enter a positive (or null) int:  " ) )
   while  x < 0:
       try:
           x = int( input( "Invalid number: Please try again: " ) )
       except ValueError:
           print( "Invalid entry.  Try again!" )
   return x