def authorize_redirect(self, callback_uri=None, extra_params=None):
if callback_uri and getattr(self, "<STR_LIT>", False):<EOL><INDENT>raise Exception("<STR_LIT>")<EOL><DEDENT>http = httpclient.AsyncHTTPClient()<EOL>if getattr(self, "<STR_LIT>", "<STR_LIT>") == "<STR_LIT>":<EOL><INDENT>http.fetch(self._oauth_request_token_url(callback_uri=callback_uri,<EOL>extra_params=extra_params),<EOL>self.async_callback(<EOL>self._on_request_token,<EOL>self._OAUTH_AUTHORIZE_URL,<EOL>callback_uri))<EOL><DEDENT>else:<EOL><INDENT>http.fetch(self._oauth_request_token_url(), self.async_callback(<EOL>self._on_request_token, self._OAUTH_AUTHORIZE_URL, callback_uri))<EOL><DEDENT>
Redirects the user to obtain OAuth authorization for this service.

        Twitter and FriendFeed both require that you register a Callback
        URL with your application. You should call this method to log the
        user in, and then call get_authenticated_user() in the handler
        you registered as your Callback URL to complete the authorization
        process.

        This method sets a cookie called _oauth_request_token which is
        subsequently used (and cleared) in get_authenticated_user for
        security purposes.