httpclient.py 文件源码

def __new__(cls, io_loop=None, max_clients=10, force_instance=False, 
                **kwargs):
        io_loop = io_loop or IOLoop.instance()
        if cls is AsyncHTTPClient:
            if cls._impl_class is None:
                from tornado.simple_httpclient import SimpleAsyncHTTPClient
                AsyncHTTPClient._impl_class = SimpleAsyncHTTPClient
            impl = AsyncHTTPClient._impl_class
        else:
            impl = cls
        if io_loop in impl._async_clients() and not force_instance:
            return impl._async_clients()[io_loop]
        else:
            instance = super(AsyncHTTPClient, cls).__new__(impl)
            args = {}
            if cls._impl_kwargs:
                args.update(cls._impl_kwargs)
            args.update(kwargs)
            instance.initialize(io_loop, max_clients, **args)
            if not force_instance:
                impl._async_clients()[io_loop] = instance
            return instance