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---------------------------------  start  --------------------------------------

@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}

---------------------------------  end ----------------------------------------