CodePattern/16 其它/对象设计模式/观察者.py

import collections  
from abc import ABC, abstractmethod  
from cppy.cp_util import *

# 定义观察者接口 ，在 Pyhon中并不是必须
class Observer(ABC):  
    @abstractmethod  
    def update(self, word):  
        pass  
  
# 定义具体观察者类，用于统计词频  
class WordFrequencyObserver(Observer):  
    def __init__(self):  
        self.word_count = collections.Counter()          
  
    def update(self, word):  
        self.word_count[word] += 1  
  
    def get_top_n(self,n):  
        return self.word_count.most_common(n)  
  
# 定义主题类  
class WordSubject:  
    def __init__(self):  
        self.observers = []  
  
    def attach(self, observer):  
        self.observers.append(observer)  
  
    def notify(self, word):  
        for observer in self.observers:  
            observer.update(word)  
  
  
# 主函数  
def main(testfilepath, top_n = 10 ):  
    stopwords = get_stopwords()  
    subject = WordSubject()  
  
    # 创建一个观察者并附加到主题  
    observer = WordFrequencyObserver()  
    subject.attach(observer)  
  
    # 处理文件      
    wordlist = re_split( read_file(testfilepath) )
    for word in wordlist:  
        if word not in stopwords:  
            subject.notify(word)  
  
    # 打印最高的N个词频  
    top_words = observer.get_top_n(top_n)  
    print_word_freqs(top_words)
    
  
if __name__ == "__main__":          
    main( testfilepath )