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Python Python Collections (2016, retired 2019) Lists Shopping List Take Three

Movrard Herard
PLUS
Movrard Herard
Courses Plus Student 543 Points

adding two items instead of one in program

whenever i add an item to the list it is added twice. I cant understand why.

import os

shopping_list = []

def clear_screen(): os.system("cls" if os.name == "nt" else "clear")

def show_help(): clear_screen() 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 add_to_list(item): show_list() if len(shopping_list): position = input("Where should I add {}?\n" "Press ENTER to add to the end of the list\n" "> ".format(item)) else: position = 0

try:
    position = abs(int(position))
except ValueError:
    position = None
if position is not None:
    shopping_list.insert(position-1, item)
else:
    shopping_list.append(new_item)
show_list

shopping_list.append(new_item)
print("Added! List has {} items.".format(len(shopping_list)))

def show_list(): clear_screen() print("Here's your list:")

index = 1
for item in shopping_list:
    print("{}. {}".format(index, item))
    index += 1


print("-"*10)

show_help()

while True: new_item = input("> ")

if new_item.upper() == 'DONE' or new_item.upper() == "QUIT":
    break
elif new_item.upper() == 'HELP':
    show_help()
    continue
elif new_item.upper() == 'SHOW':
    show_list()
    continue
else:
    add_to_list(new_item)

show_list()

1 Answer

Steven Parker
Steven Parker
216,017 Points

It's hard to read unformatted code, but the issue seems to happen on these lines:

if position is not None:
    shopping_list.insert(position-1, item)   # this line may add the item the first time
else:
    shopping_list.append(new_item)           # ...or this one will
show_list

shopping_list.append(new_item)               # then this line adds it again

In future questions, use the instructions for code formatting in the Markdown Cheatsheet pop-up below the "Add an Answer" area. :arrow_heading_down:   Or watch this video on code formatting.