我试图使一个购物清单，但每次我删除一个项目，它留下了一个很大的差距，看起来很尴尬，请有人能帮助，我仍然是非常新的这一切，我只学了一两个月，所以一个简单的答案将是非常感谢：

def subtract(user):
    x = 0
    while x == False:
        answer = input("What would you like to subtract?")
        if answer in user:
            user = user.replace(answer,"")
            y = 0
            print("your list is:" + user)
            add_or_subtract(user)
            x == True
            break
        else:
            print ("sorry, I do not recognise this, please try again.")

def add(user):
    x = 0
    while x == False:
        answer = input(str("what would you like to add?".lower()))
        if answer in user:
            print ("sorry, this is already in the list")
        else:
            user = user + "\n" + answer
            print ("Your list is: " + user)
        answer = input("are you finished adding?".lower())
        if answer in ("yes", "yea", "ye"):
            answer1 = input("do you want to subtract or finish?")
            if answer1 in ("subtract"):
                subtract(user)
                x == True
                break
            elif answer1 in ("finish"):
                print (user)
                x == True
                break
            else:
                print("Sorry I do not recognise this")

def add_or_subtract(user):
    x = 0
    while x == False:
        answer = input ("do you want to add or subtract or finish?".lower())
        if answer in ("add","addition"):
            add(user)
            x == True
            break
        elif answer in ("subtract","takeaway"):
            subtract (user)
            x == True
            break
        elif answer in ("complete", "finish"):
            print ("your final list is: " + user)
            x == True
            break
        else:
            print ("sorry i do not recognise this")
        
        
def initial(user):
    x = 0
    while x == False:
        user = input("please type out your first item:".lower())
        content = input(str("your first item is "+ user + " are you content with that?".lower()))
        if content in "no":
            user = ""
            continue
        elif content in "yes":
            add_or_subtract(user)
            x == True
            break
                        
                        
shopping = ""
initial(shopping)

还有，有没有更好的方法来做到这一点，我觉得有，我可以使用一个列表来记录所有的项目，有没有一种方法，我可以存储现有的列表到一个数据库，然后在更新时重用它？