list.remove(x): x 不在列表中使用 while 循环

Question

Scenario :

Using the list sandwich_orders from Exercise 7-8, make sure the sandwich pastrami appears in the list at least three times. Add code near the beginning of your program to print a message saying the deli has run out of pastrami , and then use a while loop to remove all occurrences of pastrami from sandwich_orders . Make sure no pastrami sandwiches end up in finished_sandwiches .

Code I have written :

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}")

below is the Error after executing the code :

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

If you already pop the last 'pastrami' sandwich, its not longer in the list, lst.pop

Notice that you don't change current_sandwich anywere, so its also a infinate loop

btw, while current_sandwich will make you to get exception, cause you will be poping an empty list

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}")