Python类继承，attributeError

我用Python编写了一个

StateMachine

类，这样就可以从中继承。 它的逻辑按预期工作，但我可以从名为

StateMachineTest

的派生

StateMachine

类中存在的

StateMachineTest

状态访问属性

self.data

生成以下错误：

Traceback (most recent call last): File "/home/nbout/work/python/state_machine/main.py", line 68, in main() File "/home/nbout/work/python/state_machine/main.py", line 59, in main test = StateMachineTest() File "/home/nbout/work/python/state_machine/main.py", line 47, in __init__ StateMachine.__init__(self, Started()) File "/home/nbout/work/python/state_machine/state_machine.py", line 17, in _init__ self.current_state.on_enter(self) File "/home/nbout/work/python/state_machine/main.py", line 16, in on_enter print("Started: data:{}".format(sm_test.data)) Started: on_enter AttributeError: 'StateMachineTest' object has no attribute 'data' Started: on_exit main.py

from state_machine import StateMachine
from state_machine import State


class StateTest(State):
    def pause(self, state_machine_test):
        pass

    def start(self, state_machine_test):
        pass


class Started(StateTest):
    def on_enter(self, sm_test):
        print("Started: on_enter")
        print("Started: data:{}".format(sm_test.data))

    def on_exit(self, sm_test):
        print("Started: on_exit")

    def pause(self, sm_test):
        print("Started: pause")
        sm_test.set_state(Paused())

    def start(self, sm_test):
        print("Started: start")


class Paused(StateTest):
    def on_enter(self, sm_test):
        print("Paused: on_enter")

    def on_exit(self, sm_test):
        print("Paused: on_exit")

    def pause(self, sm_test):
        print("Paused: pause")

    def start(self, sm_test):
        print("Paused: start")
        sm_test.set_state(Started())


class StateMachineTest(StateMachine):

    def __init__(self):
        StateMachine.__init__(self, Started())
        self.data = 10

    def pause(self):
        self.current_state.pause(self)

    def start(self):
        self.current_state.start(self)


def main():

    test = StateMachineTest()

    test.start()
    test.pause()
    test.pause()
    test.start()


if __name__ == '__main__':
    main()

---

哇，这个代码真的太复杂了

问题似乎是您在StateMachineTest类的

\uuuu init\uuuu

中初始化了

start

，以便在设置

self.data

之前，其

on\u enter

运行

---

您可以通过将

self.data

的赋值移动到

super

调用上方来解决此问题，但更好的办法是简化继承层次结构。

您的问题在于

StateMachine.\uuu初始化（self，start（））

要求已设置

self

的

data

属性，但只能在下一行设置它（

self.data=10

）。切换这两条线路，然后重试

这就是解决方案，谢谢。我会尽快接受你的回答让我…谢谢，那是我的问题。我以这种方式使用继承来强制

StateMachine

类的可重用性

from state_machine import StateMachine
from state_machine import State


class StateTest(State):
    def pause(self, state_machine_test):
        pass

    def start(self, state_machine_test):
        pass


class Started(StateTest):
    def on_enter(self, sm_test):
        print("Started: on_enter")
        print("Started: data:{}".format(sm_test.data))

    def on_exit(self, sm_test):
        print("Started: on_exit")

    def pause(self, sm_test):
        print("Started: pause")
        sm_test.set_state(Paused())

    def start(self, sm_test):
        print("Started: start")


class Paused(StateTest):
    def on_enter(self, sm_test):
        print("Paused: on_enter")

    def on_exit(self, sm_test):
        print("Paused: on_exit")

    def pause(self, sm_test):
        print("Paused: pause")

    def start(self, sm_test):
        print("Paused: start")
        sm_test.set_state(Started())


class StateMachineTest(StateMachine):

    def __init__(self):
        StateMachine.__init__(self, Started())
        self.data = 10

    def pause(self):
        self.current_state.pause(self)

    def start(self):
        self.current_state.start(self)


def main():

    test = StateMachineTest()

    test.start()
    test.pause()
    test.pause()
    test.start()


if __name__ == '__main__':
    main()