帮我写段python代码在这段代码while sp_obj < 0:#就是如果子问题的目标函数值小于0，人家才会迭代的意思吗？ route_sequence.append(new_path) pi,obj= rmp(customer_number,route_sequence) sp_obj,new_path,new_path_cost,x_mat =sp(customer_number,vertex_number,ready_time,due_time,vehicle_capacity, vehicle_number,demand,B,pi) 上加上当迭代次数为1000次时，停止，输出结果

是的，您的理解是正确的。当子问题的目标函数值小于0时，代码会继续迭代。

以下是加入迭代次数限制的代码：

MAX_ITERATIONS = 1000
iteration = 0

while sp_obj < 0 and iteration < MAX_ITERATIONS:
    route_sequence.append(new_path)
    pi, obj = rmp(customer_number, route_sequence)
    sp_obj, new_path, new_path_cost, x_mat = sp(customer_number, vertex_number, ready_time, due_time, vehicle_capacity, vehicle_number, demand, B, pi)
    iteration += 1

if iteration == MAX_ITERATIONS:
    print("Reached maximum number of iterations.")
else:
    # Output results
    print("SP objective function value: ", sp_obj)
    print("New path: ", new_path)
    print("New path cost: ", new_path_cost)
    print("x_mat: ", x_mat)

此代码将在子问题的目标函数值小于0和迭代次数小于1000时继续迭代。如果达到迭代次数限制，代码将输出“Reached maximum number of iterations.”，否则将输出计算得到的结果。