This won't work?

shoplist = []
import sys

def helps():
    print("Enter DONE to finish your list and see it \n"
          "Enter SHOW to see your list \n"
         )
def clear():
    if os.name == 'nt':
        os.system('cls')
    else:
        os.system('clear')


while len(shoplist) < 20:

    try:
        item = input("> ").lower()
        if len(item) > 15 or len(item) <= 1:
            raise ValueError("That item is too long to spell or is too short")
            continue
        elif not item.isalpha():
            raise ValueError("Thats a number not an item..")
            continue


    except ValueError as err:
        ("Something has gone wrong. {}.".format(err))



    else:

        shoplist.append()
        print("shoplist")
else:
    print("you have reached the limit of 20 items")
    sys.exit()