python中的for循环跳过[重复]

Question

我在 python 3.4 中有一个如下的 for 循环

def checkCustometers(self):
    for customer in self.customers_waiting:
        if customer.Source == self.location: #if the customer wants to get on at this floor,
            self.customers_inside_elevators.append(customer) #place customer into elevator
            self.customers_waiting.remove(customer) #The customer isent waiting anymore

比如说在

customer_waiting[4]
    if customer.Source == Self.location

然后循环删除

customer_waiting[4] 和 customer_waiting[5]

然后转到位置 4。然后循环继续并查看 customer_waiting[5] 但它实际上是在查看 customer_waiting[6] 跳过 customer_waiting[5]

我该如何解决这个问题？

Answer 1

您需要复制或使用反转：

def checkCustometers(self):
    for customer in self.customers_waiting[:]:
        if customer.Source == self.location: #if the customer wants to get on at this floor,
            self.customers_inside_elevators.append(customer) #place customer into elevator
            self.customers_waiting.remove(customer)

使用反转：

def checkCustometers(self):
    for customer in reversed(self.customers_waiting):
        if customer.Source == self.location: #if the customer wants to get on at this floor,
            self.customers_inside_elevators.append(customer) #place customer into elevator
            self.customers_waiting.remove(customer)

永远不要在不复制或使用反向的情况下改变你正在迭代的列表，否则你最终会跳过元素，正如你已经看到的那样，如果你删除一个元素，你会改变当你开始迭代时 python 指向某个特定位置的元素.

Answer 2

如果您在迭代列表时尝试改变列表，预计会看到这样的结果。

换一种干净的方式怎么样：

def checkCustometers(self):
    self.customers_inside_elevators += [c for c in self.customers_waiting if c.Source == self.location]
    self.customers_waiting = [c for c in self.customers_waiting if c.Source != self.location]