Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

Python Python Basics (2015) Shopping List App Refactor

Didier Borel
Didier Borel
2,837 Points

main() function

I don't understand what is wrong here? is it a question of indentation? Also what is the purpose of the main() function? what is its utility?

thxs

shopping_list.py
def show_help():
    # print out instructions 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(shopping_list):
    # print out the list
    print("Here's your list:")

    for item in shopping_list:
        print(item)

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

     show_help()

    # make a list to hold onto our items
    shopping_list = []

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

    # be able to quit the app
      if new_item == 'DONE':
        break
      elif new_item == 'HELP':
        show_help()
        continue
      elif new_item == 'SHOW':
        show_list(shopping_list)
        continue
      add_to_list(shopping_list, new_item)

    show_list(shopping_list)

1 Answer

Hi Didier

Your error is you have not created a function named main. You create a function with the def keyword. Refactoring is when you clean up code to make it more efficient and to prevent any repetition. In this instance the challenge asks you to put all code from the show_help function and below into its own function called main. The purpose of this is to enable your app to run over and over again as required. Say you wanted to give the usual an option to start the app again, you could call the main function and the code from the show_help and below will be called. Hope this helps

def show_help():
    # print out instructions 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(shopping_list):
    # print out the list
    print("Here's your list:")

    for item in shopping_list:
        print(item)

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

def main():
  show_help()

  # make a list to hold onto our items
  shopping_list = []

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

    # be able to quit the app
    if new_item == 'DONE':
        break
    elif new_item == 'HELP':
        show_help()
        continue
    elif new_item == 'SHOW':
        show_list(shopping_list)
        continue
    add_to_list(shopping_list, new_item)

  show_list(shopping_list)