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Python

Posted by Tiger Rahman
Tiger Rahman
1,333 Points

Removing items from the list

My list is working just fine but curious about a better way to have a user remove a list. I had a friend try it out (who doesn't code) and the first thing she asked was "How do I fix a mistake I made?" Fair enough.

I added a few things:

review the list before deciding whether or not to continue

   def review_list():
        print_list()
        print("Add more items to your list. Type 'DONE' when finished.")

be able to remove an item

    elif new_item == 'REMOVE':
        print_list()
        trash = input("What would you like to remove? ")
        shopping_list.remove(trash)
        review_list()
        continue

This all works just fine, but I can't help but wonder how this would best work to allow the user to more explicitly state what they wanted to remove (using the actual list index). I don't know that this is functionally necessary for this case, but if sequence mattered for some reason ("Apples must be item 5 on the list!"!) then there's no way to support this kind of neurosis -- except I'm sure there is.

Thoughts?

2 Answers

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,468 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,468 Points

Are you looking to enable removing items by index or by name? You can use enumerate in print_list to output items and indexes then if trash is int, pop(trash), otherwise use remove

If you wish to keep existing item at current indexes (apples st #5) then replace deleted item with shopping_list[index(trash)] = None or shopping_list[trash] = None If index provided by user.

You can test for user providing input using: 

try:
    # covert to int
    Idx = int(trash)
    # code here using idx as index
except:
    # not int, treat as item

What else were you looking for?

Tiger Rahman
Tiger Rahman
1,333 Points

Solid. Ran into a few things but checking out documentation helped! [https://docs.python.org/3.4/tutorial/errors.html] [https://docs.python.org/2/library/functions.html?highlight=enumerate#enumerate]

# print out the list
def print_list():
    print("Here's your list:")
    for new_item in enumerate(shopping_list):
        print(new_item)

# be able to remove an item
    elif new_item == 'REMOVE':
        print_list()
        trash = input("What item number would you like to remove? ")
        try:
            idx = int(trash)
            shopping_list.pop(idx)
            review_list()
            continue
        except ValueError:
            print("Sorry, I can't delete that. Returning you to your list.")
            review_list()
            print("To 'REMOVE', enter the number that appears to the left of the item you want to remove.") 
            continue

Might look into the caps-sensitivity later but learned a lot from this for today. Thanks for the assists!

Jeff Wilton
Jeff Wilton
16,646 Points
Jeff Wilton
Jeff Wilton
16,646 Points

You are on the right track, and I applaud you (and your friend) for thinking beyond the given assignment. I encourage you to go to the source (so to speak) and look at the official Python documentation on data structures:

https://docs.python.org/3.6/tutorial/datastructures.html

Something like this might be what you are looking for:

list.pop([i])

This will remove the item at the given position in the list, and return it (though you don't need to do anything with the returned value).

I think if this application had a fancy user interface, I would probably want to click on a specific item in order to remove it from the list, and therefore the index is what I would recommend using to remove (pop) the item from the list. I suppose even in a text-based UI it would still be easier to type in an index rather than the whole name of the item to remove.

Hope this helps!