如何正确使用 python += 运算符？

Question

我正在尝试使用 += 运算符，但我一直得到不正确的结果。我们在一家沙龙有一位美发师，为她的顾客提供服务。每天，她有 6 个预约时间，每次预约之间的时间间隔是相等的。如果她设法预约了某个时段，我们用变量 1 表示，如果她找不到该时段的客户，那么我们用变量 0 表示。

Appointments_Booked = [1, 0, 1, 1, 1]  # Where 1 indicates an appointment booked and 0 no appointment booked.

def service_time():
    service = random.normalvariate(5, 1)  # The time the hair dresser takes to service her customers follows a normal distribution, the hair dresser takes around 5 minutes on average to service each customer
    return service

def wait_time():
    waiting_time_last_customer = 0  # The waiting time of the first customer is zero because there is no customer booked before him or her
    interval_time_between_slots = 5  # This is how much time we have between each appointment
    y = 0
    for x in Appointments_Booked:
        if x == 1:  # If we have a customer booked for a slot
            customer_service = service_time()  #How long we will take to service a customer
            waiting_time_present_customer = max((waiting_time_last_customer + customer_service) - interval_time_between_slots, 0)  # This is the formula to compute the waiting time of the current customer. It essentially says that the waiting time of the current customer is simply the interval time (space) between appointments minus how much the previous customer had to wait for service and then get serviced.
            y += waiting_time_present_customer  # THIS IS WHERE I AM ENCOUNTERING PROBLEMS 
            print('waiting time =', y)
            print('service time =', customer_service)
        elif x == 0:
             customer_service = 0
             waiting_time_last_customer = 0
             y += waiting_time_present_customer
             print('waiting time =', y)
             print('service time =', customer_service)

我的 += 没有做我想做的事，首先我希望第一个客户的等待时间始终为 0，因为该客户不会仅仅因为在他/她之前没有其他客户而等待。其次，其他客户的结果也不同，例如，我的输出是：

waiting time = 1.449555339084272  #This does not make any sense because the first customer is supposed to have zero waiting time because they are first in line
service time = 4.400365861292478
waiting time = 0
service time = 0   # refA
waiting time = 0   # refA
service time = 4.42621491273674
waiting time = 1.0771427601173116  # The waiting time of this customer is supposed to also be zero because the service time (#refA) + waiting time(#refA) of the previous customer is zero.
service time = 6.077142760117312
waiting time = 1.0771427601173116  # The waiting time of this customer is also wrong because its supposed to be 2.154. The waiting time (1.077) + the service time (6.077) of the previous customer is 7.154 minus the interval 5 gives 2.154
service time = 4.166720282779419

我在使用 += 运算符时做错了什么，或者我做错了什么？

Answer 1

您将customer_service 添加到您的等待时间中。标准的单服务器排队模型表明：

arrival_time(i) = arrival_time(i-1) + interarrival_time  # often exponential
begin_service_time(i) = max(arrival_time(i), end_service_time(i-1))
end_service_time(i) = begin_service_time(i) + customer_service(i)

其中i 是客户编号。通过适当的初始化，您可以删除 i 并循环，因为更新仅取决于先前的值。

您已选择将其离散化为时间段，但它不会改变 a) 的基本逻辑缺陷，包括等待时间中当前客户的 customer_service，以及 b) 基于等待时间的结果之前的客户，而不是他们完成的时间。

可能还有其他缺陷，但我停止了检查，因为这些都是阻碍因素，并且您没有提供实际的驱动程序代码来运行您的模型。