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Great article. I had the misfortune of writing a bunch of twisted code over a decade ago and I wanted to remind the author that twisted has a feature called "in

Great article. I had the misfortune of writing a bunch of twisted code over a decade ago and I wanted to remind the author that twisted has a feature called "inline callbacks" that allow you to use yield. https://twisted.org/documents/16.4.1/core/howto/defer-intro.html#inline-callbacks-using-yield https://twisted.org/documents/16.4.1/core/howto/defer-intro.... So twisted code can actually look like: @inlineCallbacks def doIt(): responseBody = yield makeRequest("GET", "/users") returnValue(json.loads(responseBody)) iirc `returnValue` throws an exception of a specific type. It's ugly, but it's also the logical implementation of async on top of yield/generators.

silverdrake11 3y ago
Nowadays twisted supports this syntax: async def doIt(): responseBody = await makeRequest("GET", "/users") return json.loads(responseBody) See https://patrick.cloke.us/posts/2021/06/11/converting-twisteds-inlinecallbacks-to-async https://patrick.cloke.us/posts/2021/06/11/converting-twisted...
BiteCode_dev 3y ago
Also, asyncio started like this as well.
plq 3y ago
returnValue raises a specific exception that inlineCallbacks understands and translates to a normal return value. It was a hack that was only needed for python versions that couldn't have generators return non-None values. With modern versions, you don't need it anymore -- just use return.
zokier 3y ago
While inlineCallbacks exists, and indeed works, I would recommend not using it. I recall it not interacting with mypy particularly well, and in general being such a hack it had some annoying sharp edges. Explicit callbacks might be annoying but at least they are extremely clear on what's happening.
deleted 3y ago
[deleted]
bevenky 3y ago
This is so nostalgic. I actually met my cofounder on github due to a discussion on twisted vs gevent back in 2011. I had my inital code in twisted and he wrote the gevent piece. Fast forward 12 years and we still use gevent at http://plivo.com http://plivo.com :) Some of our initial code snippets: # Twisted def __protocolSendRaw(self, name, args=""): deferred = defer.Deferred() self.__EventQueue.append((name, deferred)) self.rawSend("%s %s" % (name, args)) return deferred # Gevent def _protocol_sendmsg(self, name, args=None, async=False): if self._closing_state: return Event() _async_res = gevent.event.AsyncResult() _uuid, event = _async_res.get() return event
- kldx 3y ago
  Off topic: PLIVO, the norwegian term actually is a protocol used by critical services here. Thought you might find it interesting :) > PLIVO (an abbreviation for ongoing life-threatening violence) is a procedure for cooperation between the police, the fire service, the rescue service and the healthcare system in incidents where life-threatening violence is perpetrated against several people.
  - bevenky 3y ago
    Nice, did not know this.. Plivo in latvian means flying high, thats was one of the languages we named it based on.
- joshxyz 3y ago
  damn i had memories of using plivo back in 2012 2013 2014
lelandbatey 3y ago
My last job (2019 - 2022) was in part shepherding a 2013-era Python 2 Tornado-and-Motor (yes the async implementation of the MongoDB driver for Python) application into Python 3 and such modern niceties. Absolutely fuck yield-raise based async implementations. Just remembering those induces psychic damage; implementing async as a massive hack on top of the language is impressive but also the kind of thing we're going to whisper to junior engineers as scary campfire stories for DECADES.

silverdrake11 3y ago

Nowadays twisted supports this syntax: async def doIt(): responseBody = await makeRequest("GET", "/users") return json.loads(responseBody) See https://patrick.cloke.us/posts/2021/06/11/converting-twisteds-inlinecallbacks-to-async https://patrick.cloke.us/posts/2021/06/11/converting-twisted...

BiteCode_dev 3y ago

Also, asyncio started like this as well.

plq 3y ago

returnValue raises a specific exception that inlineCallbacks understands and translates to a normal return value. It was a hack that was only needed for python versions that couldn't have generators return non-None values. With modern versions, you don't need it anymore -- just use return.

zokier 3y ago

While inlineCallbacks exists, and indeed works, I would recommend not using it. I recall it not interacting with mypy particularly well, and in general being such a hack it had some annoying sharp edges. Explicit callbacks might be annoying but at least they are extremely clear on what's happening.

deleted 3y ago

[deleted]

bevenky 3y ago

This is so nostalgic. I actually met my cofounder on github due to a discussion on twisted vs gevent back in 2011. I had my inital code in twisted and he wrote the gevent piece. Fast forward 12 years and we still use gevent at http://plivo.com http://plivo.com :) Some of our initial code snippets: # Twisted def __protocolSendRaw(self, name, args=""): deferred = defer.Deferred() self.__EventQueue.append((name, deferred)) self.rawSend("%s %s" % (name, args)) return deferred # Gevent def _protocol_sendmsg(self, name, args=None, async=False): if self._closing_state: return Event() _async_res = gevent.event.AsyncResult() _uuid, event = _async_res.get() return event

kldx 3y ago
Off topic: PLIVO, the norwegian term actually is a protocol used by critical services here. Thought you might find it interesting :) > PLIVO (an abbreviation for ongoing life-threatening violence) is a procedure for cooperation between the police, the fire service, the rescue service and the healthcare system in incidents where life-threatening violence is perpetrated against several people.
- bevenky 3y ago
  Nice, did not know this.. Plivo in latvian means flying high, thats was one of the languages we named it based on.
joshxyz 3y ago
damn i had memories of using plivo back in 2012 2013 2014

lelandbatey 3y ago

My last job (2019 - 2022) was in part shepherding a 2013-era Python 2 Tornado-and-Motor (yes the async implementation of the MongoDB driver for Python) application into Python 3 and such modern niceties. Absolutely fuck yield-raise based async implementations. Just remembering those induces psychic damage; implementing async as a massive hack on top of the language is impressive but also the kind of thing we're going to whisper to junior engineers as scary campfire stories for DECADES.