为什么If/Else循环会脱离For循环？

Question

我在做一个假设很简单的python挑战，一个朋友给了我一个电梯和它运动背后的逻辑。一切都进行得很顺利，直到我不得不写下如何确定电梯是否可以移动，并在到达下一个排队楼层的途中撞上一个叫的楼层。你知道吗

def floorCompare(currentFloor,destinationFloor,calledFloor):
    if calledFloor > currentFloor and calledFloor < destinationFloor:
        return(True)
    elif calledFloor < currentFloor and calledFloor > destinationFloor:
        return(True)
    else:
        return(False)

floor = "1"
doors = "closed"
queue = []
def elevator(): # function defines how the elevator should move
    print("The Elevator is on floor: 1. The doors are "+doors+".")
    for x in range(int(input("How many floors need to be visited? "))):
        callFloor = int(input("Floor to call the elevator to: "))
        queue.append(callFloor)
        if callFloor > 10 or callFloor < 1:
            raise Exception(str(callFloor)+" is not a valid floor.")
    if queue[0] == 1:
        del queue[0]
        print("The elevator has arrived on floor 1, and the doors are open.")
    print("The queue of floors to visit is...",queue)
    for x in queue:
        print("The elevator's doors are closed and it's moving to floor:",x)
        floor = str(x)
        print("...")
        print()
        print("The elevator has arrived on floor "+floor+", and the doors are open.")
        queue.remove(x)
        addFloor = int(input("Floor to call the elevator to: "))
        if addFloor > 10 or addFloor < 1:
            raise Exception(str(addFloor)+" is not a valid floor.")
        print(queue)
        if floorCompare(int(floor), int(queue[0]), int(addFloor)) == True:
            print("The elevator can hit this stop en route to its next one.")
        else:
            print("The elevator must hit this stop separately.")
    print("Continuing Queue")

elevator()

所以在For循环中，有一个嵌套的If/Else循环，我假设它将与For循环中的其余代码一起迭代。但是，当我运行代码时，在到达If/Else循环时，它会跳出For循环，继续它的快乐之路，而忽略了需要在数组中进行的任何进一步迭代。这是怎么回事？你知道吗

当我用一个基本的楼层测试集运行代码时，下面是我得到的输出。你知道吗

The Elevator is on floor: 1. The doors are closed.
How many floors need to be visited? 4
Floor to call the elevator to: 3
Floor to call the elevator to: 6
Floor to call the elevator to: 9
Floor to call the elevator to: 10
The queue of floors to visit is... [3, 6, 9, 10]
The elevator's doors are closed and it's moving to floor: 3
...

The elevator has arrived on floor 3, and the doors are open.
Floor to call the elevator to: 7
[6, 9, 10]
The elevator must hit this stop seperately.
The elevator's doors are closed and it's moving to floor: 9
...

The elevator has arrived on floor 9, and the doors are open.
Floor to call the elevator to: 3
[6, 10]
The elevator must hit this stop separately.

Process finished with exit code 0

Answer 1

提前退出的原因是，您在列表上循环时正在修改列表。举个简单的例子：

l = [3,6,9,10]

for x in l:
    print(x)
    l.remove(x)

输出为

3
9

但是，当前代码还有许多其他问题。我能抓住的是：

1. 您没有在for循环中添加新调用的楼层。你知道吗
2. 用queue[0]作为目标调用floorCompare方法，而不是final方法。如您所见，由于您比较了3和6，因此7没有被认为是在途中。你应该比较3和10，最远的一个。你知道吗

还要注意，queue最初没有排序，中间调用也不会按顺序排列。所以你在使用它的时候要记住这一点。你知道吗

Answer 2

我认为您的问题在于将for循环与队列.删除（）功能。似乎for x in queue:操作符在运行时编辑列表时遇到了问题。我建议改为使用while queue:，并将x设置为第一个元素。你知道吗

    while queue:
        x = queue[0]
        print("The elevator's doors are closed and it's moving to floor:",x)
        floor = str(x)
        print("...")
        print()
        print("The elevator has arrived on floor "+floor+", and the doors are open.")
        queue.remove(x)
        addFloor = int(input("Floor to call the elevator to: "))
        if addFloor > 10 or addFloor < 1:
            raise Exception(str(addFloor)+" is not a valid floor.")
        print(queue)
        if floorCompare(int(floor), int(queue[0]), int(addFloor)) == True:
            print("The elevator can hit this stop en route to its next one.")
        else:
            print("The elevator must hit this stop separately.")

Answer 3

它之所以跳过第6层，是因为从正在迭代的列表中删除了数据。你知道吗

l=[3,6,9,10,14]
for i in l:
    print(i)

输出： 三 6 9 10 14个

for i in l:
    print(i)
    l.remove(i)

输出： 三 9 14个