Shopping list what is wrong in my code when I run the file I get the below error I'm using pycharm

#Creating a shopping list
shopping_list = []
# SHOW for list of items in the list
def show_items():
    for items in shopping_list:
        print(items)

#HELP for showing special commands
def help():
    print ("DONE for quitting adding to the list")
    print ("HELP for help information")
    print ("SHOW for list of items in the list")
def add_items():
    shopping_list.append(user_input)

while True:
    # Take user input and add items to the list
    user_input = input("Enter the items : ")
    add_items()
    if user_input == 'SHOW':
        show_items()
        continue
    elif user_input == 'HELP':
        help()
        continue
    # DONE for quitting app
    elif user_input == 'DONE':
        break
    add_items()

Enter the items : dkjasfk
Traceback (most recent call last):
  File "C:/Users/Somasx/PycharmProjects/Treehouse/Shopping-List.py", line 20, in <module>
    user_input = input("Enter the items : ")
  File "<string>", line 1, in <module>
NameError: name 'dkjasfk' is not defined