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Python Python Basics All Together Now Handle Exceptions

Posted by Erik Embervine
.a{fill-rule:evenodd;}techdegree
Erik Embervine
Python Development Techdegree Student 2,442 Points

is Craig's code in the masterticket.py program considered "clean" or "complete"?

after Craig completes his finishing touches to the code in this video, i ran the code again. when i enter a string value to answer the question "How many tickets would you like?", it outputs not only the "Sorry not valid" print statement in the "except ValueError as err" block, which makes sense, but it also prints out the contents of the "err" variable: "invalid literal for int() with base 10: [string]". is this what Craig intended? i assume we don't want users to see this.. maybe i missed something? i came up with my own solution to handle the message, but was curious if i am mistaken, or if this was an oversight or by design? other?

Erik Embervine
.a{fill-rule:evenodd;}techdegree
Erik Embervine
Python Development Techdegree Student 2,442 Points

FYI, this is how I solved it myself, but am wondering if there is a better/more efficient way...

TICKET_PRICE = 10
SERVICE_CHARGE = 2
tickets_remaining = 100

def calculateTotal(ticketCount):
    return ticketCount * TICKET_PRICE + SERVICE_CHARGE

def masterticket(TICKET_PRICE,tickets_remaining):
    print("There is/are ",tickets_remaining," tickets left!")
    newVisitor = input("What is your name?  ")
    while True:
        try:
            ticketCount = int(input("How many tickets would you like, "+newVisitor+"?"))
            #handle numbers out of range
            if ticketCount > 100 or ticketCount < 0:
                print("Sorry we don't have that many...")
                continue
            elif ticketCount > tickets_remaining:
                print("Sorry we don't have that many..")
                continue
            break
        #handle string value exceptions
        except ValueError:
            ticketCount = print("Sorry, I need you to give me a number...")
            continue
    totalPrice = calculateTotal(ticketCount)
    print("Ok, your total comes to: $",totalPrice)
    purchaseConfirmation = input("Do you want to proceed with purchase?  Y/N:  ")
    if purchaseConfirmation.startswith('y' or 'Y'):
        tickets_remaining -= ticketCount
        print("Thanks for your purchase!")
    else:
        print("No problem, thanks for visiting!")
    return tickets_remaining

tickets_left = masterticket(TICKET_PRICE,tickets_remaining)

while tickets_left > 0:
    tickets_left = masterticket(TICKET_PRICE,tickets_left)

print("Monty Python Show Tickets are SOLD OUT!!!")

1 Answer

Steven Parker
Steven Parker
231,271 Points
Steven Parker
Steven Parker
231,271 Points

I think you can expect that every course exercise will be designed to illustrate the lesson principles but none will be examples of fully implemented and rigidly tested ready-to-publish software products.

The fact that all the examples may be efficiency optimized, UX enhanced, or given additional features can become opportunities for extra practice if you want some.

As to improvements, this line of the code caught my eye:

    if purchaseConfirmation.startswith('y' or 'Y'):

You can't combine terms with logic operators, only complete expressions. This won't detect a capital "Y". But you can do it with complete expressions like this:

    if purchaseConfirmation.startswith('y') or purchaseConfirmation.startswith('Y')::

But perhaps more efficiently like this:

    if purchaseConfirmation.lower().startswith('y'):

Also, testing for ticketCount above 100 or less than 0 isn't necessary, since neither is a possible condition.

Erik Embervine
.a{fill-rule:evenodd;}techdegree
Erik Embervine
Python Development Techdegree Student 2,442 Points

thank you!

Erik Embervine
.a{fill-rule:evenodd;}techdegree
Erik Embervine
Python Development Techdegree Student 2,442 Points

actually it seems i can enter -100 for the ticket count and is accepted, because ticketCount isn't handled anywhere for values less than 0 and it's different than the tickets remaining variable...

so i added this:

TICKET_PRICE = 10
SERVICE_CHARGE = 2
tickets_remaining = 100

def calculateTotal(ticketCount):
    return ticketCount * TICKET_PRICE + SERVICE_CHARGE

def masterticket(TICKET_PRICE,tickets_remaining):
    print("There is/are ",tickets_remaining," tickets left!")
    newVisitor = input("What is your name?  ")
    while True:
        try:
            ticketCount = int(input("How many tickets would you like, "+newVisitor+"?"))
            #handle numbers higher than remaining tickets.  we've already handled tickets < 0 in a previous while loop
            if ticketCount > tickets_remaining or ticketCount <= 0:
                print("Sorry we don't have that many..")
                continue
            break
        #handle string value exceptions
        except ValueError:
            ticketCount = print("Sorry, I need you to give me a number...")
            continue
    totalPrice = calculateTotal(ticketCount)
    print("Ok, your total comes to: $",totalPrice)
    purchaseConfirmation = input("Do you want to proceed with purchase?  Y/N:  ")
    if purchaseConfirmation.lower() == 'y':
        tickets_remaining -= ticketCount
        print("Thanks for your purchase!")
    else:
        print("No problem, thanks for visiting!")
    return tickets_remaining

tickets_left = masterticket(TICKET_PRICE,tickets_remaining)

while tickets_left > 0:
    tickets_left = masterticket(TICKET_PRICE,tickets_left)

print("Monty Python Show Tickets are SOLD OUT!!!")

....i think it's solid now...