在函数内定义一个类来中断装饰器的执行

Question

I'm trying to configure a decorator at run time. This is somewhat related to my earlier question: How to configure a decorator in Python

The motivation for this is that I'm trying to use the Thespian troupe code "as-is".

Is it legal to have this code here, where I've defined the class (and therefore called the decorator) inside a class method? Again, the reason for this is that I could feed the max_count argument prior to the decorator being call.

The module is calculator.calculator (yes, bad choice perhaps)

class Scheduler:
    def __init__(self):
        self.actor_system = None

    def start(self):
        self.actor_system = ActorSystem('multiprocTCPBase')

    def stop(self):
        self.actor_system.shutdown()

    def launch(self, count, func_and_data, status_cb):
        class CalcPayload:
            def __init__(self, func_and_data, status_cb):
                self.func_and_data = func_and_data
                self.status_cb = status_cb

        @troupe(max_count=count)
        class Execute(ActorTypeDispatcher):
            def receiveMsg_CalcPayload(self, msg, sender):
                func = msg.func_and_data['func']
                data = msg.func_and_data['data']
                status_cb = msg.status_cb

                self.send(sender, func(data, status_cb))

        exec_actor = self.actor_system.createActor(Execute)

        for index in range(len(func_and_data)):
            calc_config = CalcPayload(func_and_data[index], status_cb)
            self.actor_system.tell(exec_actor, calc_config)

        for index in range(len(func_and_data)):
            result = self.actor_system.listen(timeout)

        self.actor_system.tell(exec_actor, ActorExitRequest())

For various reasons, I can't apply the decorator to the class when I use it. There is a brief discussion on this in the question I referenced.

Answer 1

While not invalid, it is generally inadvisable to define a class as a local variable inside a function, as it would make access to the class difficult outside the function.

Instead, you can define the classes outside the function, and apply the decorator function to the class when it's actually needed by calling the decorator function with the class object:

class CalcPayload:
    def __init__(self, func_and_data, status_cb):
        self.func_and_data = func_and_data
        self.status_cb = status_cb


class Execute(ActorTypeDispatcher):
    def receiveMsg_CalcPayload(self, msg, sender):
        func = msg.func_and_data['func']
        data = msg.func_and_data['data']
        status_cb = msg.status_cb

        self.send(sender, func(data, status_cb))

class Scheduler:
    def __init__(self):
        self.actor_system = None

    def start(self):
        self.actor_system = ActorSystem('multiprocTCPBase')

    def stop(self):
        self.actor_system.shutdown()

    def launch(self, count, func_and_data, status_cb):
        exec_actor = self.actor_system.createActor(troupe(max_count=count)(Execute))

        for index in range(len(func_and_data)):
            calc_config = CalcPayload(func_and_data[index], status_cb)
            self.actor_system.tell(exec_actor, calc_config)

        for index in range(len(func_and_data)):
            result = self.actor_system.listen(timeout)

        self.actor_system.tell(exec_actor, ActorExitRequest())

Answer 2

The actor_system is going to want to build instances of your class. That means it needs to be able to derive the class object- you cannot define it inside of a method.

If you really need to apply the decorator separately, you maybe could do

def launch(self, count, func_and_data, status_cb):
    wrapped = troupe(max_count=count)(Executor)
    exec_actor = self.actor_system.createActor(wrapped)