Question

我正在制作为用户构建购物清单的程序。这应该反复询问用户的项目，直到他们进入＆＃39;结束＆＃39;然后它应该打印列表。如果用户已经添加了项目，则下次应该忽略该项目。我遇到了问题，最后一部分应该忽略重复。我也需要使用＆＃39;继续＆＃39;但不知道如何实现我的代码。

shoppingListVar = []
while True:
    item = input("Enter your Item to the List: ")
    shoppingListVar.append(item)
    if item in item:
        print("you already got this item in the list")
    if item == "end":
        break
print ("The following elements are in your shopping list:")
print (shoppingListVar)

Answer 1

您最好在代码中使用if-elif-else结构来处理3种不同的预期条件

您还需要将if item in item:更改为if item in shoppingListVar:

shoppingListVar = []
while True:
    item = input("Enter your Item to the List: ")
    if item in shoppingListVar:
        print("you already got this item in the list")
    elif item == "end":
        break
    else:
        shoppingListVar.append(item)
print ("The following elements are in your shopping list:")
print (shoppingListVar)

Answer 2

应为if item in shoppingListVar:。

shoppingListVar = []
while True:
    item = input("Enter your Item to the List: ")
    if item == "end":
        break

    if item in shoppingListVar:
        print("you already got this item in the list")
        continue

    shoppingListVar.append(item)

print ("The following elements are in your shopping list:")
print (shoppingListVar)

此代码在将新项目附加到列表之前首先检查sentinel值（'end'），如果它尚未存在。

如果购物清单的顺序无关紧要，或者您要对其进行排序，则可以使用set代替list。这将照顾重复项，您无需检查它们，只需使用shopping_list.add(item)（并使用shopping_list = set()进行初始化）

shopping_list = set()
while True:
    item = input("Enter your Item to the List: ")
    if item == "end":
        break
    shopping_list.add(item)

print("The following elements are in your shopping list:")
print(shopping_list)

相同的输入两次不输入两次

2 个答案: