2.编写程序并测试，有一个汽车类 Vehicle，类中的私有数据成员为车轮个数 wheels 和车重 weight；小车类 Car 是汽车类 vehicle 派生类，其中包含载客人数 passenger_load，默认 4 人；卡车类 Truck 是汽车类 vehicle 派生类，其中包含载 客人数 passenger_load 和载重量 payload。 提示：编写类时要使用 get 和 set 方法，Vehicle 类定义 display()显示车轮 和重量，Car 和 Truck 中要对 display()进行同名覆盖。

好的，以下是符合您要求的 Python 代码：

class Vehicle:
    def __init__(self, wheels, weight):
        self._wheels = wheels
        self._weight = weight
    
    def get_wheels(self):
        return self._wheels
    
    def set_wheels(self, wheels):
        self._wheels = wheels
    
    def get_weight(self):
        return self._weight
    
    def set_weight(self, weight):
        self._weight = weight
    
    def display(self):
        print("Number of wheels:", self._wheels)
        print("Weight:", self._weight, "kg")
        
class Car(Vehicle):
    def __init__(self, wheels, weight, passenger_load=4):
        super().__init__(wheels, weight)
        self._passenger_load = passenger_load
    
    def get_passenger_load(self):
        return self._passenger_load
    
    def set_passenger_load(self, passenger_load):
        self._passenger_load = passenger_load
    
    def display(self):
        super().display()
        print("Passenger load:", self._passenger_load)
        
class Truck(Vehicle):
    def __init__(self, wheels, weight, passenger_load, payload):
        super().__init__(wheels, weight)
        self._passenger_load = passenger_load
        self._payload = payload
    
    def get_passenger_load(self):
        return self._passenger_load
    
    def set_passenger_load(self, passenger_load):
        self._passenger_load = passenger_load
    
    def get_payload(self):
        return self._payload
    
    def set_payload(self, payload):
        self._payload = payload
    
    def display(self):
        super().display()
        print("Passenger load:", self._passenger_load)
        print("Payload:", self._payload, "kg")

您可以使用以下代码进行测试：

# test Vehicle class
vehicle = Vehicle(4, 1000)
vehicle.display()

# test Car class
car = Car(4, 800)
car.display()
car.set_passenger_load(5)
car.display()

# test Truck class
truck = Truck(6, 5000, 2, 10000)
truck.display()
truck.set_passenger_load(3)
truck.set_payload(8000)
truck.display()

输出如下：

Number of wheels: 4
Weight: 1000 kg
Number of wheels: 4
Weight: 800 kg
Passenger load: 4
Number of wheels: 4
Weight: 800 kg
Passenger load: 5
Number of wheels: 6
Weight: 5000 kg
Passenger load: 2
Payload: 10000 kg
Number of wheels: 6
Weight: 5000 kg
Passenger load: 3
Payload: 8000 kg