Class AsyncHTTPClient

python/python3/tornado/httpclient.py:140–336

An non-blocking HTTP client. Example usage:: async def f(): http_client = AsyncHTTPClient() try: response = await http_client.fetch("http://www.google.com") except Exception as e: print("Error: %s" % e) els

class AsyncHTTPClient(Configurable):
    """An non-blocking HTTP client.

    Example usage::

        async def f():
            http_client = AsyncHTTPClient()
            try:
                response = await http_client.fetch("http://www.google.com")
            except Exception as e:
                print("Error: %s" % e)
            else:
                print(response.body)

    The constructor for this class is magic in several respects: It
    actually creates an instance of an implementation-specific
    subclass, and instances are reused as a kind of pseudo-singleton
    (one per `.IOLoop`). The keyword argument ``force_instance=True``
    can be used to suppress this singleton behavior. Unless
    ``force_instance=True`` is used, no arguments should be passed to
    the `AsyncHTTPClient` constructor. The implementation subclass as
    well as arguments to its constructor can be set with the static
    method `configure()`

    All `AsyncHTTPClient` implementations support a ``defaults``
    keyword argument, which can be used to set default values for
    `HTTPRequest` attributes.  For example::

        AsyncHTTPClient.configure(
            None, defaults=dict(user_agent="MyUserAgent"))
        # or with force_instance:
        client = AsyncHTTPClient(force_instance=True,
            defaults=dict(user_agent="MyUserAgent"))

    .. versionchanged:: 5.0
       The ``io_loop`` argument (deprecated since version 4.1) has been removed.

    """

    _instance_cache = None  # type: Dict[IOLoop, AsyncHTTPClient]

    @classmethod
    def configurable_base(cls) -> Type[Configurable]:
        return AsyncHTTPClient

    @classmethod
    def configurable_default(cls) -> Type[Configurable]:
        from tornado.simple_httpclient import SimpleAsyncHTTPClient

        return SimpleAsyncHTTPClient

    @classmethod
    def _async_clients(cls) -> Dict[IOLoop, "AsyncHTTPClient"]:
        attr_name = "_async_client_dict_" + cls.__name__
        if not hasattr(cls, attr_name):
            setattr(cls, attr_name, weakref.WeakKeyDictionary())
        return getattr(cls, attr_name)