为什么multiprocess.Process不能调用getattr方法？

Question

尝试通过multiprocessing.Process中的getattr()调用say_hello和say_world两个方法，但尚未执行say_world方法。我怎么才能让它成为可能呢？谢谢。

# -*- coding: utf-8 -*-
from multiprocessing import Process
import time

class Hello:
    def say_hello(self):
        print('Hello')

    def say_world(self):
        print('World')


class MultiprocessingTest:
    def say_process(self, say_type):
        h = Hello()
        while True:
            if hasattr(h, say_type):
                    result = getattr(h, say_type)()
                    print(result)
            time.sleep(1)

    def report(self):
        Process(target=self.say_process('say_hello')).start()
        Process(target=self.say_process('say_world')).start() # This line hasn't been executed.


if __name__ == '__main__':
    t = MultiprocessingTest()
    t.report()

Answer 1

参数target需要一个对函数的引用作为值，但您的代码将None传递给它。以下是需要更改的部分：

class Hello:
    def say_hello(self):
        while True:
            print('Hello')
            time.sleep(1)

    def say_world(self):
        while True:
            print('World')
            time.sleep(1)

class MultiprocessingTest:
    def say_process(self, say_type):
        h = Hello()
        if hasattr(h, say_type):
            return getattr(h, say_type) # Return function reference instead of execute function
        else:
            return None