在 Python 中访问变量时运行代码

Question

我有一个类人。 如果在 Person.sitting == True 时访问了它的 running_speed 变量，则它必须抛出 SittingError。

class SittingError(Exception):
    pass

class Person:
    def __init__(self):
        self.sitting = False
        self.running_speed = 4

bob = Person()
print(bob.running_speed) # Works fine, he's not sitting
bob.sitting = True
print(bob.running_speed) # Throws SittingError, as running_speed was accessed while sitting

我该如何实现？

Answer 1

您可以使用@property装饰器并在 getter 中抛出异常，如果sitting == true 。

class SittingError(Exception):
    pass

class Person:
    def __init__(self):
        self.sitting = False
        self._running_speed = 4

    @property
    def running_speed(self):
        if self.sitting:
            raise SittingError()
        return self._running_speed

    @running_speed.setter
    def running_speed(self, speed):
        self._running_speed = speed

bob = Person()
print(bob.running_speed) # Works fine, he's not sitting
bob.sitting = True
print(bob.running_speed)