rest_view.py

async def author(request):
    """Return a single author for a given id."""

    connection = request.app['connection']

    with log_request(request):
        try:
            
            # when using co-routines, it's important that each co-routine be non-blocking
            # meaning no individual action will take a long amount of time, preventing
            # the event loop from letting other co-routines execute
            
            # since our database query may not immediately return, we run it
            # in an "executor" (a thread pool) and await for it to finish
            
            # functools.partial allows us to create a callable that
            # bundles necessary positional and keyword arguments with it
            # in a way that is pickle-able https://docs.python.org/3/library/pickle.html
            
            # i.e. `print('hello', end=' ') == partial(print, 'hello', end= ' ')()`
                        
            db_query = partial(
                fetch_authors, connection, id=int(request.match_info['id']))
            
            # * unpacks an arbitrary number of tuples (see pep-3132)

            author, *_ = await request.loop.run_in_executor(None, db_query)

        except ValueError:
            author = None

        if not author:
            log_message('Author not found', id=request.match_info['id'])
            raise web.HTTPNotFound

    response = web.json_response(author)

    with log_response(response):
        return response