Python下HttpHTTPClient和AsyncHTTPClient

HTTPClient 使用例子：

    from tornado.httpclient import HTTPClient 
 
 def synchronous_fetch(url): 
　　　　　http_client = HTTPClient() 
　　　　　response = http_client.fetch(url) 
　　　　 return response.body

AsyncHTTPClient使用例子：

方法1：
    from tornado.httpclient import AsyncHTTPClient 

 def asynchronous_fetch(url, callback): 
　 http_client = AsyncHTTPClient() 
 def handle_response(response): # 创建一个函数内的函数，来处理返回的结果
 callback(response.body) 
 http_client.fetch(url, callback=handle_response)   # 异步处理结束后会调用指定的callback的函数


方法2：
    from tornado.httpclient import AsyncHTTPClient 
    from tornado.concurrent import Future 

 def async_fetch_future(url): 
 http_client = AsyncHTTPClient() 
 my_future = Future() 
 fetch_future = http_client.fetch(url) 
 fetch_future.add_done_callback(lambda f: my_future.set_result(f.result())) 
 return my_future

方法3：
    from tornado.httpclient import AsyncHTTPClient 
    from tornado import gen 

 @gen.coroutine #添加异步访问的装饰器
 def fetch_coroutine(url): 
 http_client = AsyncHTTPClient() 
 response = yield http_client.fetch(url) # 获取异步结果时要使用yield 
 raise gen.Return(response.body)  # 使用抛出异常的方式来返回结果，不能使用return来返回


以下知识是额外的可以了解下，但不保证知识是完整的：
　　async and await 在python3.5，tornado4.3中可以了解下 
 
　　例子：
  async deffetch_coroutine(url): 
　　 http_client = AsyncHTTPClient()
 response = await http_client.fetch(url) 
 return response.body

 
使用yield来遍历异步的结果是，以下方法是在项目中没有试验过的
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@gen.coroutine
def parallel_fetch(url1, url2): resp1, resp2 = yield [http_client.fetch(url1), http_client.fetch(url2)] @gen.coroutine def parallel_fetch_many(urls): responses = yield [http_client.fetch(url) for url in urls] # responses is a list of HTTPResponses in the same order @gen.coroutine def parallel_fetch_dict(urls): responses = yield {url: http_client.fetch(url) for url in urls} # responses is a dict {url: HTTPResponse}

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