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Python Python Basics All Together Now Handle Exceptions

Posted by David Accomazzo
David Accomazzo
15,986 Points

How would I throw a user-friendly error for the number of tickets not being a string?

Code looks like this so far:

try:
    num_tickets = input("How many tickets would you like, {}?  ".format(name))
    num_tickets = int(num_tickets)
    # Raise a ValueError if the request is for more tickets than are available
    if num_tickets > tickets_remaining:
        raise ValueError('There are only {} tickets remaining.'.format(tickets_remaining))
except ValueError as err:
    # include the error text in the output
    print("Oh no, we ran into an issue. {}. Please try again.".format(err))

How do we throw an error if int(num_tickets) throws a ValueError? I'm not sure what the syntax for that looks like in Python. Currently it just throws the generic error message if num_tickets is a string. I would like to have it throw something like "You must enter a number, not letters, here!"

2 Answers

Steven Parker
Steven Parker
231,172 Points
Steven Parker
Steven Parker
231,172 Points

One way would be to peek at the contents of the message that would be issued, and replace it with a custom message instead:

except ValueError as err:
    if ("invalid literal" in str(err)):
        # use custom message for bad characters
        print("You must enter a number, not letters, here!")
    else:
        # include the error text in the output
        print("Oh no, we ran into an issue.  {}  Please try again.".format(err))
David Accomazzo
David Accomazzo
15,986 Points
David Accomazzo
David Accomazzo
15,986 Points

Sounds good to me! Thanks