行为型模式

观察者模式 (Observer pattern)

在对象之间定义一对多的依赖, 这样一来, 当一个对象改变状态, 依赖它的对象都会收到通知, 并自动更新。

class Observer:
    """
    观察者
    """
    def __init__(self, name):
        self.name = name

    def update(self, msg):
        print(self.name + "收到信息：" + msg)


class Subject:
    """
    主题
    """
    def __init__(self):
        self.observers = []

    def add_observers(self, observer):
        self.observers.append(observer)
        return self

    def remove_observer(self, observer):
        self.observers.remove(observer)
        return self

    def notify(self, msg):
        for observer in self.observers:
            observer.update(msg)


xiaoming = Observer("xiaoming")
lihua = Observer("lihua")

rain = Subject()
# 添加订阅
rain.add_observers(xiaoming)
rain.add_observers(lihua)

rain.notify("下雨了！")

# 取消订阅
rain.remove_observer(lihua)

rain.notify("打雷了！")

连接池模式

class QueueObject():
    def __init__(self, queue, auto_get=False):
        self._queue = queue
        self.object = self._queue.get() if auto_get else None

    def __enter__(self):
        if self.object is None:
            self.object = self._queue.get()
        return self.object

    def __exit__(self, type, value, traceback):
        if self.object is not None:
            self._queue.put(self.object)
            self.object = None

    def __del__(self):
        if self.object is not None:
            self._queue.put(self.object)
            self.object = None


def main():
    try:
        import queue
    except ImportError:  # python 2.x compatibility
        import Queue as queue

    def test_object(queue):
        queue_object = QueueObject(queue, True)
        print('Inside func: {}'.format(queue_object.object))

    sample_queue = queue.Queue()

    sample_queue.put('yam')
    with QueueObject(sample_queue) as obj:
        print('Inside with: {}'.format(obj))
    print('Outside with: {}'.format(sample_queue.get()))

    sample_queue.put('sam')
    test_object(sample_queue)
    print('Outside func: {}'.format(sample_queue.get()))

    if not sample_queue.empty():
        print(sample_queue.get())


if __name__ == '__main__':
    main()

更多设计模式：http://www.pythontip.com/pythonPatterns/