list.remove(x): x 不在列表中使用 while 循环

Question

场景：

使用列表sandwich_orders练习7-8，确保三明治pastrami出现在列表中至少三次。 在程序开头附近添加代码以打印一条消息，说明熟食店的pastrami已用完，然后使用 while 循环从sandwich_orders pastrami删除所有出现的pastrami 。 确保没有pastrami三明治最终出现在finished_sandwiches 。

我写的代码：

sandwich_orders=['egg&mayo','cheese&onion','chicken&sweetcorn','pastrami','pastrami',
'egg&watercress','pastrami','pastrami']
finished_sandwiches=[ ]

current_sandwich=sandwich_orders.pop()

print(f"\nYour Sandwich has been prepared : {current_sandwich}")

while current_sandwich:

    print(f"\nCurrent sandwich is {current_sandwich}!!")

    if current_sandwich=='pastrami':
        sandwich_orders.remove('pastrami')
        print(f"\n{current_sandwich} has been removed from the orders")
    else:
        finished_sandwiches.append(current_sandwich)
        print(f"\nYour Sandwich has been prepared : {current_sandwich}")
print(f"\nList of finshed swandwiches : {finished_sandwiches}")

print(f"\nList of Sandwich Orders recieved : {sandwich_orders}")

以下是执行代码后的错误：

Traceback (most recent call last):
  File "C:\Users\thota01\AppData\Local\Programs\Python\Python38\Python_Input_whileLoops\movietickets.py", line 9, in <module>
    sandwich_orders.remove('pastrami')

**ValueError: list.remove(x): x not in list**

Answer 1

如果你已经lst.pop了最后一个“ lst.pop ”三明治， lst.pop不再在列表中了， lst.pop

请注意，您没有更改 current_sandwich，因此它也是一个无限循环

顺便说一句， while current_sandwich会让你得到异常，因为你会弹出一个空列表

sandwich_orders=['egg&mayo','cheese&onion','chicken&sweetcorn','pastrami','pastrami',
'egg&watercress','pastrami','pastrami']
finished_sandwiches=[ ]

print(f"\nYour Sandwich has been prepared : {current_sandwich}")
while sandwich_orders:
    current_sandwich = sandwich_orders.pop()
    print(f"\nCurrent sandwich is {current_sandwich}!!")
    if current_sandwich=='pastrami':
        print(f"\n{current_sandwich} has been removed from the orders")
    else:
        finished_sandwiches.append(current_sandwich)
        print(f"\nYour Sandwich has been prepared : {current_sandwich}")
print(f"\nList of finshed swandwiches : {finished_sandwiches}")

print(f"\nList of Sandwich Orders recieved : {sandwich_orders}")