if we answer != int at spot then it gives and error and i couldnt fixed it by try/except can u show me the way pls

#!/usr/bin/python
shopping_list = []

def show_help():
    print("\nSeperate items with a comma.")
    print("Press DONE to quit, SHOW to see your current shopping list and HELP to see this.")

def show_list():
    count = 1
    for item in shopping_list:
        print("{}: {}".format(count, item))
        count += 1

print("Give me a list of things that you want to shop.")
show_help()

while True:
    new_stuff = input("> ")

    if new_stuff == "DONE":
        print("\nHere is your shopping list.")
        show_list()
        break
    elif new_stuff == "HELP":
        show_help()
        continue
    elif new_stuff == "SHOW":
        show_list()
        continue
    else:
        new_list = new_stuff.split(",")
        index = input("Add this item to a certain place? Press Enter to add at the end, " "or give me a number. Currently {} items are on the list: ".format( len(shopping_list)))

    try:
        if index:
            spot = int(index) - 1 
            for item in new_list:
                shopping_list.insert(spot, item.strip())
                spot += 1
        else:
            for item in new_list:
                shopping_list.append(item.strip())
    except ValueError:
        print("Input index {} is not allowed.".format(index))

$ python3 tmp.py 
Give me a list of things that you want to shop.

Seperate items with a comma.
Press DONE to quit, SHOW to see your current shopping list and HELP to see this.
> a
Add this item to a certain place? Press Enter to add at the end, or give me a number. Currently 0 items are on the list: r
Input index r is not allowed.
> DONE

Here is your shopping list.