[littlePilot]

I am having lots of trouble trying to get this code to loop... is there a easy way.... i have the number of books looping but i just cant get the discount if there a book shop or not.... like just if someone types in eg apple it just crashes... i just want it to loop till it gets a yes or no... and then work from there

def restart_program():
    pass
while True:
    try:
        books = float (input("So how many books do u want?"))
        break
    except ValueError:
        pass
    print ("that was not a number")


discount = input('do you own a book shop?(yes or no)')


book_cost = 24.95
shipping = 3
extra_shiping = 0.75
extra_discount = .6
if discount == 'yes':
    print ("$",(books * book_cost) *(extra_discount)+(books * extra_shiping) - (extra_shiping) + shipping)
elif discount == 'no':
    print ("$",(books * book_cost)+(books * extra_shiping) - (extra_shiping) + shipping)

[atraub]

Hey, welcome to DreamInCode. I think this little function is exactly what you want.

def userSaidYes(message):
    response = ""
    while response not in ["yes","no"]:
        response = input(str(message) +" (yes or no) ").lower()
    return response == "yes"

if the user enters "yes" it will return true, if he says no, it will return false. If he says something else, it'll just ask him again. Also, I automatically take whatever the user enters and make it lowercase. If I didn't do that "Yes" would cause it to fail. This function is fairly versatile, you might be able to use it again. For this situation, it would look like this in use userSaidYes('do you own a book shop?').

Here's a similar function I gave to another member a little while ago, you might find it useful for getting the number of books the user wants. There's a lot of comments because some people are less familiar with try/except blocks.

def getInput(inputString, expectedType, errorString = False ):
    while True: #Continue indefinitely
        try: #try to do this, but an error could hit

            #use input to communicate the inputString to the user and return the result after it's been casted to the type you're looking for
            return expectedType(input(inputString)) 

        except ValueError as e:#This is error handling
            if errorString:#if you provided an errorString
                print(errorString) #print it
            else: #otherwise
                print (str(e)) #print the default python error
            print ("Please try again\n")

if you don't mind my 2 cents, here's how I would rewrite this program to be a little cleaner

Spoiler

def main():
    books = getInput("So, how many books do u want? ", int, "that was not a whole number")
    book_cost = 24.95
    shipping = 3
    extra_shiping = 0.75
    extra_discount = .6
    if userSaidYes('do you own a book shop? '):
        print ("$",(books * book_cost) *(extra_discount)+(books * extra_shiping) - (extra_shiping) + shipping)
    else:
        print ("$",(books * book_cost)+(books * extra_shiping) - (extra_shiping) + shipping)

def userSaidYes(message):
    response = ""
    while response not in ["yes","no"]:
        response = input(str(message) +" (yes or no) ").lower()
    return response == "yes"

def getInput(inputString, expectedType, errorString = False ):
    while True: #Continue indefinitely
        try: #try to do this, but an error could hit

            #use input to communicate the inputString to the user and return the result after it's been casted to the type you're looking for
            return expectedType(input(str(inputString))) 

        except ValueError as e:#This is error handling
            if errorString:#if you provided an errorString
                print(errorString) #print it
            else: #otherwise
                print (str(e)) #print the default python error
            print ("Please try again\n")

if __name__ == "__main__":
    main()

You'll notice that I use int instead of float for books. I do that because I think it would be weird for a customer to say "I want 4.2 books." You can change it back if you disagree

Also, all your code is now inside of functions... nice, modular, reusable functions. When you run your code in the shell it will still run automatically, but if you want to run it again, you can type main() and it will.

That last line if __name__ == "__main__": thing might look weird. If you're curious about it or why I use it, here's the wikipedia article that describes it. Basically, if you import this program into another module, it won't automatically run, but if you run it on its own, it will.

This post has been edited by atraub: 07 March 2012 - 08:48 PM
Reason for edit:: added spoiler tags. He might not want my 2 cents lol

[littlePilot]

lol sorry about posting what u siad twice i am not used to using this web site... and i know i took awhile to thank you but i havnt had a chance... and thanks for your 2 cents since i am new to python i try and learn all i can by looking at your code... so thanks for everything (i wish i was as good as programing as you )

This post has been edited by atraub: 04 October 2012 - 06:25 AM
Reason for edit:: removed the double quote

[atraub]

I'm glad it helped you out!

littlePilot, on 04 October 2012 - 03:51 AM, said:

(i wish i was as good at programing as you )

We all have to start from somewhere. There are people out there who make me look like a bewildered jackass but we both just have to keep at it and strive to be the best we can.