我如何子类threading.Event？

Question

在Python 2.7.5中:

from threading import Event

class State(Event):
    def __init__(self, name):
        super(Event, self).__init__()
        self.name = name

    def __repr__(self):
        return self.name + ' / ' + self.is_set()

我明白了:

TypeError:调用元类base
函数时出错()参数1必须是代码,而不是str

为什么？

我所知道的关于线程的一切.事件我从以下网站学习:http://docs.python.org/2/library/threading.html？highlight = threading # event-objects

当它说threading.Event()是类threading.Event ???的工厂函数时它是什么意思？(呃......看起来对我很平常).

Answer 1

threading.Event不是一个类,它在threading.py中的功能

def Event(*args, **kwargs):
    """A factory function that returns a new event.

    Events manage a flag that can be set to true with the set() method and reset
    to false with the clear() method. The wait() method blocks until the flag is
    true.

    """
    return _Event(*args, **kwargs)

Sinse这个函数返回_Event实例,你可以子类_Event(尽管导入和使用下划线名称绝不是一个好主意):

from threading import _Event

class State(_Event):
    def __init__(self, name):
        super(Event, self).__init__()
        self.name = name

    def __repr__(self):
        return self.name + ' / ' + self.is_set()