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<h1 id="-" style="margin: 20px 0px 10px; padding: 0px; font-weight: bold; color: black; font-size: 24px; border-bottom: 2px solid #aaaaaa;">一.行为型模式
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<p style="margin: 0.5em 0px !important; font-size: 16px; line-height: 1.75em; padding-right: 0.5em; padding-left: 0.5em;">创建型模式基于对象的创建机制，隔离了对象的创建细节，使代码能够与要创建的对象的类型相互独立

 abc  ABCMeta,abstractmethod
<span class="hljs-class"><span class="hljs-keyword" style="color: #ebbbff;">class <span class="hljs-title" style="color: #7285b7;">NewsPublisher:           <span class="hljs-comment" style="color: #7285b7;">#subject

<span class="hljs-function" style="color: #bbdaff;"><span class="hljs-keyword" style="color: #ebbbff;">def <span class="hljs-title" style="color: #7285b7;">init<span class="hljs-params" style="color: #ffc58f;">(self):

self.subscribers = []

self.latestNews = <span class="hljs-keyword" style="color: #ebbbff;">None
<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;attach</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self,subscriber)</span>:</span>
    self.__subscribers.append(subscriber)

<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;detach</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    <span class="hljs-keyword" style="color: #ebbbff;"&gt;return</span> self.__subscribers.pop()

<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;notifySubscribers</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    <span class="hljs-keyword" style="color: #ebbbff;"&gt;for</span> sub <span class="hljs-keyword" style="color: #ebbbff;"&gt;in</span> self.__subscribers:
        sub.update()

<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;addNews</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self,news)</span>:</span>
    self.__latestNews = news

<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;getNews</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    <span class="hljs-keyword" style="color: #ebbbff;"&gt;return</span> <span class="hljs-string" style="color: #d1f1a9;"&gt;'Got News:'</span>+self.__latestNews
<span class="hljs-class"><span class="hljs-keyword" style="color: #ebbbff;">class <span class="hljs-title" style="color: #7285b7;">Subscriber<span class="hljs-params" style="color: #ffc58f;">(metaclass=ABCMeta):       <span class="hljs-comment" style="color: #7285b7;">#Observer
<span class="hljs-decorator"&gt;@abstractmethod</span>
<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;update</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    <span class="hljs-keyword" style="color: #ebbbff;"&gt;pass</span>
<span class="hljs-class"><span class="hljs-keyword" style="color: #ebbbff;">class <span class="hljs-title" style="color: #7285b7;">ConcreteSubscriber1:           <span class="hljs-comment" style="color: #7285b7;">#ConcreteObserver

<span class="hljs-function" style="color: #bbdaff;"><span class="hljs-keyword" style="color: #ebbbff;">def <span class="hljs-title" style="color: #7285b7;">init<span class="hljs-params" style="color: #ffc58f;">(self,publisher):

self.publisher=publisher

self.publisher.attach(self)
<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;update</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    print(type(self).__name__,self.publisher.getNews())
<span class="hljs-class"><span class="hljs-keyword" style="color: #ebbbff;">class <span class="hljs-title" style="color: #7285b7;">ConcreteSubscriber2:

<span class="hljs-function" style="color: #bbdaff;"><span class="hljs-keyword" style="color: #ebbbff;">def <span class="hljs-title" style="color: #7285b7;">init<span class="hljs-params" style="color: #ffc58f;">(self,publisher):

self.publisher = publisher

self.publisher.attach(self)
<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;update</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self)</span>:</span>
    print(type(self).__name__,self.publisher.getNews())
news_publisher = NewsPublisher()

<span class="hljs-keyword" style="color: #ebbbff;">for Subscribers <span class="hljs-keyword" style="color: #ebbbff;">in [ConcreteSubscriber1,ConcreteSubscriber2]:  <span class="hljs-comment" style="color: #7285b7;">#创建观察者对象

Subscribers(news_publisher)
news_publisher.addNews(<span class="hljs-string" style="color: #d1f1a9;">'HELLO WORLD')

news_publisher.notifySubscribers()

news_publisher.detach()

news_publisher.addNews(<span class="hljs-string" style="color: #d1f1a9;">'SECOND NEWS')

news_publisher.notifySubscribers()

<span class="hljs-string" style="color: #d1f1a9;">'''

ConcreteSubscriber1 Got News:HELLO WORLD

ConcreteSubscriber2 Got News:HELLO WORLD

ConcreteSubscriber1 Got News:SECOND NEWS

'''

<p style="margin: 0px 0px 1.2em !important; font-size: 16px; line-height: 1.75em; padding-right: 0.5em; padding-left: 0.5em;">上面的代码应该很容易就读懂了，但是拉模型在这里是什么意思呢，先看一下拉模型的含义：

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<p style="margin: 0.5em 0px !important; font-size: 16px; line-height: 1.75em; padding-right: 0.5em; padding-left: 0.5em;">每当发生变化时，主题都会向所有已经注册的观察者进行广播

<span class="hljs-class"><span class="hljs-keyword" style="color: #ebbbff;">class <span class="hljs-title" style="color: #7285b7;">ConcreteSubscriber2:
<span class="hljs-function" style="color: #bbdaff;"><span class="hljs-keyword" style="color: #ebbbff;">def <span class="hljs-title" style="color: #7285b7;">init<span class="hljs-params" style="color: #ffc58f;">(self,publisher):
self.publisher = publisher
self.publisher.attach(self)

<span class="hljs-function" style="color: #bbdaff;"&gt;<span class="hljs-keyword" style="color: #ebbbff;"&gt;def</span> <span class="hljs-title" style="color: #7285b7;"&gt;update</span><span class="hljs-params" style="color: #ffc58f;"&gt;(self,news)

news_publisher = NewsPublisher()
<span class="hljs-keyword" style="color: #ebbbff;">for Subscribers <span class="hljs-keyword" style="color: #ebbbff;">in [ConcreteSubscriber1,ConcreteSubscriber2]: <span class="hljs-comment" style="color: #7285b7;">#创建观察者对象
Subscribers(news_publisher)

news_publisher.addNews(<span class="hljs-string" style="color: #d1f1a9;">'HELLO WORLD')
news_publisher.notifySubscribers()
news_publisher.detach()
news_publisher.addNews(<span class="hljs-string" style="color: #d1f1a9;">'SECOND NEWS')
news_publisher.notifySubscribers()

<span class="hljs-string" style="color: #d1f1a9;">'''
ConcreteSubscriber1 HELLO WORLD
ConcreteSubscriber2 HELLO WORLD
ConcreteSubscriber1 SECOND NEWS
'''

<p style="margin: 0px 0px 1.2em !important; font-size: 16px; line-height: 1.75em; padding-right: 0.5em; padding-left: 0.5em;">这里只将update函数添加了传递的数据参数，并在notifySubscribers函数中传递了参数。

<p style="margin: 0px 0px 1.2em !important; font-size: 16px; line-height: 1.75em; padding-right: 0.5em; padding-left: 0.5em;">这种方式只有一个步骤就是主题发送数据，所以能够提高性能，但缺点就是观察者会获得可能自己不需要的数据，当有大量数据观察者都用不到的话就会很浪费了，使响应时间过长。两种方式各有利弊

<h1 id="-" style="margin: 20px 0px 10px; padding: 0px; font-weight: bold; color: black; font-size: 24px; border-bottom: 2px solid #aaaaaa;">四.观察者模式的优缺点

（编辑：李大同）

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