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Python Python Basics (Retired) Shopping List Shopping List Project

Dhruv Ghulati
Dhruv Ghulati
1,582 Points

How to take comma separated inputs for list, challenge part 2?

First part of challenge solved via:


For the second part, would I include error handling via:

if not ',' in input('>'):, print('You have an invalid input'), else shopping_list.append(new_item)?

3 Answers

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

Your error handling, as written, requires that the input must have a comma. Does this mean you wish to not allow adding items one at a time?

Instead of checking for a comma on the input, you can simply split() the input into a list. The code below captures input into new_items then adds them to the shopping_list. Note the use of extend() instead of append() since split() returns a list:

new_items = input('>')

If the input is a single item, split simply returns a list consisting of that one item. Caution: split only removes the splitting character. If you split on comma and the user includes spaces then the spaces will be part of the item string. It will take more code to handle both cases of commas and commas+spaces. Perhaps removing all spaces before splitting or parsing the input with a intermediate Python regular expression

Marni Kostman
Marni Kostman
7,558 Points

chris freeman Here is the code I just came up with. It may have some spacing issues but it only uses the functions we have learned up to this point in Kenneth's videos.

shopping_list = [] #could also use list() function

print("What should we pick up at the store?")
print("Enter 'DONE' to stop adding items.")

while True: #true is never a reason to stop...will go on forever
  new_item=input("> ")

  if new_item == "DONE":
    break #breaks the loop

  new_item=new_item.split(", ")

  for item in new_item:

  print("Added! List has {} items.".format(len(shopping_list)))
  continue #continues the loop/starts over

print("Here's your list:")

for item in shopping_list: #don't have to call them "items" - can call them anything - all elements of container, when we get to last item in list, loop stops

I originally just added the line with split but, when I did that, it was counting the whole entry as 1 item. When I added the extra "for" loop, the "Added!" line worked and accurately counted items.

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

Looks Good! Three critiques::

  • The continue statement is not required at the end of a while block. Continue is the default action at the end of the code block
  • You're correct on using "item" over "items" for the iterating variable name since it refers to a singular 'thing' from the reference sequence shopping_list
  • new_item might be better named as new_items or items_list to indicate it is a sequence. The statement then becomes more readable as for item in new_items: ....
  • If user enters a blank item, the empty item will be added to the list. You may wish to add a check for this case and skip adding the blank item

Keep up the good work!

Marni Kostman
Marni Kostman
7,558 Points

Thanks, chris freeman...will definitely update with your suggestions!