Python 抛出 ValueError: list.remove(x): x not in list (not iterating over list)

Question

I'm trying to solve the codewars kata of Vasya-Clerk. I'm getting the value error because I am removing items from the list. I read that I should make a copy of the list instead but since I am not iterating over the list itself but just appending and removing values it's not very clear to me how and where to do this copy with the command [:]. I know I could solve this maybe better with a dictionary but would like to finish it with lists if possible.

Here are the instructions: The new "Avengers" movie has just been released. There are a lot of people at the cinema box office standing in a huge line, Each of them has a single 100. 50 or 25 dollar bill. An "Avengers" ticket costs 25 dollars. Vasya is currently working as a clerk. He wants to sell a ticket to every single person in this line? Can Vasya sell a ticket to every person and give change if he initially has no money and sells the tickets strictly in the order people queue, Return YES. if Vasya can sell a ticket to every person and give change with the bills he has at hand at that moment. Otherwise return NO

def tickets(people):  
    cash = []
    for bill in people:
      if bill == 25:
        cash.append(bill)
      elif bill == 50:
        if 25 in cash:
          cash.append(bill)
          cash.remove(25)
        else:
          return "NO"
      elif bill == 100:
        if 25 and 50 in cash:
          cash.append(bill)
          cash.remove(25)
          cash.remove(50)
        elif 25 and 25 and 25 in cash:
          cash.append(bill)
          cash.remove(25)
          cash.remove(25)
          cash.remove(25)
        else:
          return "NO"
      else:
        return "NO"

    return "YES"

test.assert_equals(tickets([25, 25, 50]), "YES")
test.assert_equals(tickets([25, 100]), "NO")

Answer 1

Your problem is in the following two lines:

if 25 and 50 in cash:

and

elif 25 and 25 and 25 in cash:

Contrary to what it seems you assume, the first is just the same as 50 in cash and the second evaluates as 25 in cash . Instead, you want to specify the conditions properly, and count the amount of 25 in cash. They become:

if 25 in cash and 50 in cash:

and

elif cash.count(25) >= 3:

Answer 2

Following @tmrlvi Just to finish your code...

def tickets(people):
    cash = []
    for bill in people:
        if bill == 25:
            cash.append(bill)
        elif bill == 50:
            if 25 in cash:
                cash.append(bill)
                cash.remove(25)
            else:
                return "NO"
        elif bill == 100:
            if 25 in cash and 50 in cash:
                cash.append(bill)
                cash.remove(25)
                cash.remove(50)
            elif cash.count(25) >= 3:
                cash.append(bill)
                cash.remove(25)
                cash.remove(25)
                cash.remove(25)
            else:
                return "NO"
        else:
            return "NO"

    return "YES"