Program doesn't end after user types in “q” for quit outside the function - Python while loop

Question

I want the user to add new items to the list. When user enters "q", I want the program to quit and then use this list as an input for another function. But I can't break out of the loop as "Q" is added to the list:

base = ["item1", "item2"]

def add_item(item, base=base):
    item=item.upper()
    base.append(item)
    return base

while True:
    user_input = add_item(input("Add an item or enter q to finish: "))
    if user_input == "Q":
      break

    else:
       print(f"New item added: {user_input}")
print("Added")

Also, how can I later use the final output (final list) as input for another function? I would like to check if the item is already in the list, then do something with this item. I have a general idea that maybe I should use "global" like this:

def check(item):
  global base
  if item in base:
    print("in the list")
  else:
    print("not here")

Is there a better approach?

Answer 1

because user_input is the return value of your function not the actual input of the program which user typed!

in = input("Add an item or enter q to finish: ")
if in == "Q":
      break
else:
      user_input = add_item()