Python asyncio post: Reworded some things; added some PEPs

drafts/2018-03-09-python-asyncio.org

@@ -5,13 +5,29 @@ date: March 9, 2018
 tags: technobabble
 ---
 
-Recently I needed to work a little more in-depth with [[https://docs.python.org/3/library/asyncio.html][asyncio]] in
+# TODO: Generators?  Is it accurate that prior to all this, coroutines
-Python 3.x.  While some people (including me) might scoff at this
+# were still available, but by themselves they offered no way to
-because cooperative threading is a model that's fresh out of the '90s
+# perform anything in the background?
-and because Python /still/ has the [[https://wiki.python.org/moin/GlobalInterpreterLock][GIL]], it is still preferable to
+
-manually writing code in [[https://en.wikipedia.org/wiki/Continuation-passing_style][continuation-passing-style]] (that's all
+Recently I needed to work a little more in-depth with Python 3's
-callbacks are), and last time I had to write that many callbacks, I
+[[https://docs.python.org/3/library/asyncio.html][asyncio]].  On the one hand, some people (including me) might scoff at
-hated it enough that I wrote my own [[https://github.com/HaskellEmbedded/ion][EDSL]] to avoid it.  But I digress.
+this because it's just green threads and cooperative threading is a
+model that's fresh out of the '90s, and Python /still/ has the [[https://wiki.python.org/moin/GlobalInterpreterLock][GIL]] -
+and because Elixir and Erlang and Haskell and [[http://blog.paralleluniverse.co/2013/05/02/quasar-pulsar/][Clojure]] and [[http://docs.paralleluniverse.co/quasar/][Java/Kotlin]]
+have handled async and M:N threading fine.  However, it's still a
+useful enough paradigm that it's already in C via [[https://github.com/libuv/libuv][libuv]], and it's in
+the works for [[https://doc.rust-lang.org/nightly/unstable-book/language-features/generators.html][Rust]] (sort of... it had green threads which were removed
+in favor of a lighter approach) and the [[http://cr.openjdk.java.net/~rpressler/loom/Loom-Proposal.html][JVM]] (sort of... they're trying
+to do [[https://en.wikipedia.org/wiki/Fiber_(computer_science)][fibers]], not green threads).  The Python folks have their own set
+of complaints, like [[http://lucumr.pocoo.org/2016/10/30/i-dont-understand-asyncio/][I don't understand Python's Asyncio]].
+
+On the other hand, asyncio is still preferable to manually writing
+code in [[https://en.wikipedia.org/wiki/Continuation-passing_style][continuation-passing-style]] (as that's all callbacks are, and
+last time I had to write that many callbacks, I hated it enough that I
+[[https://haskellembedded.github.io/posts/2016-09-23-introducing-ion.html][added features to my EDSL]] to avoid it), it's still preferable to a lot
+of manual arithmetic on timer values to try to schedule things, and
+it's still preferable to doing blocking I/O all over the place and
+trying to escape it with other processes.
 
 I found the [[https://pymotw.com/3/concurrency.html][Concurrency with Processes, Threads, and Coroutines]]
 tutorials to be approachable and thorough, and I highly recommend
@@ -25,6 +41,7 @@ over to some other code, whereas calling "whenever" means retaining
 control but queuing up some code to be run in the background
 asychronously (as much as possible).
 
+|-----------+-----------+-----------------------+-----------------------------------------------|
 | Call from | Call to   | When/where            | How                                           |
 |-----------+-----------+-----------------------+-----------------------------------------------|
 | Either    | Function  | Now, same thread      | Normal function call                          |
@@ -35,6 +52,11 @@ asychronously (as much as possible).
 |           |           |                       | ~asyncio.ensure_future()~                     |
 | Either    | Function  | Now, another thread   | ~.run_in_executor()~ on ~ThreadPoolExecutor~  |
 | Either    | Function  | Now, another process  | ~.run_in_executor()~ on ~ProcessPoolExecutor~ |
+|-----------+-----------+-----------------------+-----------------------------------------------|
+
+# TODO: How do I make Pandoc render this table better? It's hardly
+# usable right now because you can't see where a column starts and
+# ends
 
 * Futures & Coroutines
 
@@ -62,7 +84,7 @@ The ability to make a Future from a coroutine was mentioned above;
 that's [[https://docs.python.org/3/library/asyncio-task.html#task][asyncio.Task]], an implementation of [[https://docs.python.org/3/library/asyncio-task.html#future][asyncio.Future]], but it's not
 the only way to make a Future.
 
-[[https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.Future][concurrent.futures.Future]] is another mostly-compatible way.  Its
+[[https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.Future][concurrent.futures.Future]] provides other mostly-compatible ways.  Its
 [[https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.ThreadPoolExecutor][ThreadPoolExecutor]] provides Futures based on separate threads, and its
 [[https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.ProcessPoolExecutor][ProcessPoolExecutor]] provides Futures based on separate processes.
 
@@ -90,5 +112,13 @@ There is also [[https://github.com/MagicStack/uvloop\][uvloop]].  I presently ha
 (nor could I really use it alongside Qt), but it's helpful to know
 about.
 
-# Also: What about coroutine generators?
+* Other References
-# Are they anything special?
+
+There are a couple pieces of "official" documentation that can be good
+references as well:
+
+- [[https://www.python.org/dev/peps/pep-0492/][PEP 492 - Coroutines with async and await syntax]]
+- [[https://www.python.org/dev/peps/pep-0525/][PEP 525 - Asynchronous Generators]]
+- [[https://www.python.org/dev/peps/pep-3156/][PEP 3156 - Asynchronous IO Support Rebooted: the "asyncio" Module]]
+
+[[https://www.python.org/dev/peps/pep-0492/][PEP 342]] and [[https://www.python.org/dev/peps/pep-0380/][PEP 380]] are relevant too.