negotiation.py 文件源码

def select_renderer(self, request, renderers, format_suffix=None):
        """
        Given a request and a list of renderers, return a two-tuple of:
        (renderer, media type).
        """
        # Allow URL style format override.  eg. "?format=json
        format_query_param = self.settings.URL_FORMAT_OVERRIDE
        format = format_suffix or request.query_params.get(format_query_param)

        if format:
            renderers = self.filter_renderers(renderers, format)

        accepts = self.get_accept_list(request)

        # Check the acceptable media types against each renderer,
        # attempting more specific media types first
        # NB. The inner loop here isn't as bad as it first looks :)
        #     Worst case is we're looping over len(accept_list) * len(self.renderers)
        for media_type_set in order_by_precedence(accepts):
            for renderer in renderers:
                for media_type in media_type_set:
                    if media_type_matches(renderer.media_type, media_type):
                        # Return the most specific media type as accepted.
                        media_type_wrapper = _MediaType(media_type)
                        if (
                            _MediaType(renderer.media_type).precedence >
                            media_type_wrapper.precedence
                        ):
                            # Eg client requests '*/*'
                            # Accepted media type is 'application/json'
                            full_media_type = ';'.join(
                                (renderer.media_type,) +
                                tuple('{0}={1}'.format(
                                    key, value.decode(HTTP_HEADER_ENCODING))
                                    for key, value in media_type_wrapper.params.items()))
                            return renderer, full_media_type
                        else:
                            # Eg client requests 'application/json; indent=8'
                            # Accepted media type is 'application/json; indent=8'
                            return renderer, media_type

        raise exceptions.NotAcceptable(available_renderers=renderers)