http_client.fetch(url) return response.body And here is the same function rewritten asynchronously as a native coroutine: from tornado.httpclient import AsyncHTTPClient async def asynchronous_fetch(url): http_client 15Tornado Documentation, Release 6.5.1 Native vs decorated coroutines Python 3.5 introduced the async and await keywords (functions using these keywords are also called “native corou- tines”). For compatibility you can use “decorated” or “yield-based” coroutines using the tornado.gen.coroutine decorator. Native coroutines are the recommended form whenever possible. Only use decorated coroutines when compatibility

guide Introduction Asynchronous and non-Blocking I/O Blocking Asynchronous Examples Coroutines Native vs decorated coroutines How it works How to call a coroutine Coroutine patterns Calling blocking fetch(url) return response.body And here is the same function rewritten asynchronously as a native coroutine: from tornado.httpclient import AsyncHTTPClient async def asynchronous_fetch(url): fetch(url) return response.body Native vs decorated coroutines Python 3.5 introduced the async and await keywords (functions using these keywords are also called “native coroutines”). For compatibility