How to complete the "Extra Credit" Portion of Shopping List App (Being able to save it as a text file)

def help_command(): #function to print the help menu
    print("====CURRENT SUPPORTED COMMANDS===")
    print("DELETE: Allows you to delete items from your list")
    print("HELP: Displays the help menu")
    print("SHOW: Displays current items in your list")
    print("DONE: Quits the current mode (Deletion or List Creation)")
def duplicate_input():
    print("Ooops! You have already added that item to the list!")
    print("Please continue to add items to your list or type DONE")
def blank_input():
    print("Ooops! You did not input anything")
    print("Please try your input again, or type DONE to continue adding to your list")
def print_list():
    for item in shopping_list: #for loop
        if item.lower() != "done": #if input is done
            print(str(shopping_list.index(item)+1)+":"+' '+item) #prints the list in numerical order
open("test.py" "a")
for "test.py"
    shopping_list = [] #make a list to hold onto our items
    print("Welcome to my shopping application!") #print instructions on how to use the app
    print("To use this app, enter each item you need to remember and hit Enter. When you are finished type DONE!")
    help_command()
    while True: #ask for new items
        new_item = input("> ") #add new items to our list
        if new_item.lower() == "show": #SHOW: Show all items on list 
            print("Here are the items currently on your shopping list!") #prints string
            print_list()
        elif new_item.lower() == "help": #HELP: Help Message
            help_command() #prints help_command
        elif new_item.lower() == 'delete': #DELETE: Deletes Inputted Item
            while True: #starts a while loop
                print("What item would you like to delete? PLEASE NOTE IT IS CASE SENSITIVE!") #prints that string
                deletion_item = input("> ") #allows user to set what item to delete
                if deletion_item in shopping_list: #checks to see if item is in list
                    shopping_list.remove(deletion_item) #deletes item from list
                    print(deletion_item + " has been deleted from your list.") #prints string
                    print("You may continue entering items for deletion or for type DONE to continue adding items") #prints string
                elif deletion_item == "": #if input is empty
                    blank_input() #return blank_input function
                elif deletion_item.lower() == "show": #if input is show
                    print("Here are the items currently in your list")
                    print_list() #prints current list
                elif deletion_item.lower() != "done" and deletion_item.lower() !="help" and deletion_item not in shopping_list: #checks to see if an input is in list
                    print("That item is not contained in your shopping list! Try again or type DONE to add more items") #prints string
                elif deletion_item.lower() == "help": #displays the help menu
                    help_command()
                elif deletion_item.lower() == "done": #allows the user to finish deleting
                    print("You are done deleting items, please input more items into your list, or type DONE") #prints string
                    break #ends while loop
        elif new_item in shopping_list: #Checks for duplicate items in list
            duplicate_input() #runs duplicate_input function
        elif new_item == "": #Checks for a blank input
            blank_input() #return blank_input function
        elif new_item.lower() == "done": #be able to quit the app
            break #breaks while loop 
        else:
            shopping_list.append(new_item) #adds input to list
    print("Here is your final shopping list!") #print out the list
    print_list() #prints the list in numerical order
    print("Thank you for using my application!")
file.close()