I can't identify the issue in this code. Can someone please help?

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):
        postition = 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()

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()

Here's your list:                                                                                
1. coco                                                                                          
----------                                                                                       
Where should I add apple?                                                                        
Press ENTER to add to the end of the list                                                        
>                                                                                                
Traceback (most recent call last):                                                               
  File "shopping_list_3.py", line 66, in <module>                                                
    add_to_list(new_item)                                                                        
  File "shopping_list_3.py", line 30, in add_to_list                                             
    position = abs(int(position))                                                                
UnboundLocalError: local variable 'position' referenced before assignment                        
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