Don't know how to add already loaded variables in code

I have been making a code that helps with store inventory. I have it as a Walmart store inventory. Anyways, I need help because I don’t know how to have an inventory with items already in it. I have the code working but this is as far as I can go with the current knowledge I have in coding. The inventory is set on line 43 just so you know. Thank you for your help ahead of time.

print("Walmart inventory") items = [] itemsAmount = [] def addItem(): newItem = str(input('Name the item you are adding: ')) items.append(newItem) setItemAmount = int(input("Input the amount: ")) itemsAmount.append(setItemAmount) def decision(): choice = str(input('\nPick a number on what you want to do:\n 0. Leave\n 1. View Stock\n 2. Add New Item\n 3. Remove Item\n 4. Change Item Amount\n')) if choice == "0": return False elif choice == "1": return "view" elif choice == "2": return "add" elif choice == "3": return "remove" elif choice == "4": return "change" else: print("An error occured, please try again.\n") main() def removeItem(): deletion = str(input('Input item you want to remove: ')) itemsAmount.pop(int(items.index(deletion))) items.remove(deletion) def amountChange(): change = str(input('What item amount is being changed: ')) amount = int(input("What is it being changed to: ")) if change in items: itemsAmount[items.index(change)] = amount else: print('There was an error') main() def main(): action = decision() if action == False: pass elif action == "view": #Edit for inventory here print("") for x in range(len(items)): print (items[x] + " | "+str(itemsAmount[x])) main() elif action == "add": addItem() main() elif action == "remove": removeItem() main() elif action == "change": amountChange() main() print("This program adds items to the stock of Walmart. It also has a loaded inventory so choose 1 first.") main()

I think that’s Python code.

What do you mean by having items already in it?
The simplest way I can think of is to just write stuff in the lists when you write them for the first time.

items = ["shirts", "pants"]
itemsAmount = [5, 3]

A more complex version of this would get the information from an external file, and save it to a file after updating the inventory …
that’s file input and output stuff.