Python设计模式：代理模式

# 真实对象
class WebCrawler:
    def fetch(self, url):
        print(f"爬取网页数据：{url}")

# 代理对象
class Proxy:
    def __init__(self):
        self.cache = {}
        self.crawler = WebCrawler()

    def fetch(self, url):
        if url not in self.cache:
            self.cache[url] = self.crawler.fetch(url)
        else:
            print(f"从缓存中获取数据：{url}")
        return self.cache[url]

# 客户端
if __name__ == '__main__':
    proxy = Proxy()
    proxy.fetch("pidancode.com")
    proxy.fetch("皮蛋编程")
    proxy.fetch("pidancode.com")