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Python Python Basics (2015) Shopping List App Second Shopping List App

Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points
Posted by Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points

Why my items in my list just keep incrementing by just pressing enter without typing any characters?

why is that?

markmneimneh
markmneimneh
14,132 Points

without looking at the challenge ... this means that you have something like this in the code

+=
or
++
or 
variable = variable + 1;

check you code and you should see it somewhere

Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points
Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points

nope i don't have that, i did exactly as knneth love did.

markmneimneh
markmneimneh
14,132 Points

do you mind pasting the code ?

Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points
Karl Michael Figuerrez
Karl Michael Figuerrez
963 Points 
#make a list to hold onto our items
Shopping_list = []

def show_help():
    #print out instruction on how to use the app
    print("What should we pick up at the store?")
    print("""Enter 'DONE' to stop adding items.
Enter 'HELP' for this help.
Enter 'SHOW' to see your current list""")

def show_list():
    #print out the list
    print("Here's your list: ")

    for item in Shopping_list:
        print(item)
    print("You got {} items.".format(len(Shopping_list)))

def add_to_list(new_item):
    #add new items to out list
    Shopping_list.append(new_item)
    print("Added {}. List now has {} items. ".format(new_item, len(Shopping_list)))

show_help() 

def main():
    while True: 
        #ask for new items
        new_item = input(">")

        #be able to quit the app
        if new_item == 'DONE' or new_item == 'done':
            break
        elif new_item == 'HELP' or new_item == 'help':
            show_help()
            continue
        elif new_item == 'SHOW' or new_item == 'show':
            show_list()
            continue
        add_to_list(new_item)


    show_list()

main()
markmneimneh
markmneimneh
14,132 Points

hello

look at this 

       #be able to quit the app
        if new_item == 'DONE' or new_item == 'done':
            break
        elif new_item == 'HELP' or new_item == 'help':
            show_help()
            continue
        elif new_item == 'SHOW' or new_item == 'show':
            show_list()
            continue
        add_to_list(new_item)



hint ... so what happened if your input does not meet the condition  'DONE' or new_item == 'done': 
or your input does not meet the condition  new_item == 'HELP' or new_item == 'help':
or your item does not meet the condition  elif new_item == 'SHOW' or new_item == 'show':
...
...
...
it will 
  add_to_list(new_item)

so regardless of the programming language you are using ... you need to handle the case when a user enter nothing (as in blank ... or nit enter

hope this helps

2 Answers

Brandon Kelly
Brandon Kelly
3,808 Points
Brandon Kelly
Brandon Kelly
3,808 Points

Hey there, Karl! The reason that your program adds an item to the list even though you just hit enter and didn't type anything is because Python is accepting a 'blank' as an input string. There is a method called .isalpha() that will determine whether a string is made up of alphabetic characters or not. This method returns a Boolean value(True or False). To use this method in your code you need to nest the if, elif, and else statements all within an if statement that uses the .isalpha() method.

                             Ex.:             if shopping_list.isalpha()
                                                  if new_item == "HELP"
                                                       show_help()
                                                  else:
                                                       show_list()
                                              else:
                                                   print("INVALID INPUT. MUST ENTER ALPHABETIC CHARACTERS ONLY") 

  Just an example of how that function could be used as to stop blank or numeric input. Hope this helps, I know its not quite within the scope of the lesson, but I was annoyed by my program doing the same thing and wanted to fix it.
Murali KRISHNA Devarakonda
Murali KRISHNA Devarakonda
734 Points
Murali KRISHNA Devarakonda
Murali KRISHNA Devarakonda
734 Points

The answer lies in one of the previous classes on boolean- checking for empty string. Add this to the top of your add_to_list(new_item) function.

if not (new_item):
    return