async/await and why it's awesome

An introduction to async/await and asyncio.

Transcript

1. async/await and why it’s awesome Yury Selivanov EuroPython 2016 or an introduction to 
 async/await and asyncio
2. Yury Selivanov – @1st1 About me • Co-founder of MagicStack (http://magic.io); check our company out! • Avid Python user since 2008. • CPython core developer since 2013.
3. Yury Selivanov – @1st1 What I do for Python • Co-authored and implemented PEP 362:
 inspect.signature API. • Authored and implemented PEP 492:
 async/await syntax. • Co-maintainer of asyncio with Guido and Victor Stinner. • Created uvloop & asyncpg.
4. Let’s talk about coroutines
5. Yury Selivanov – @1st1 One obvious way to do it • Callbacks and Deferreds; Twisted since 2002. • Stackless Python & greenlets. • Python 2.5: coroutines with yield. • Python 3.3: coroutines with yield from. • Python 3.5: async/await.
6. Yury Selivanov – @1st1 Coroutines: yield
7. Yury Selivanov – @1st1 Coroutines: yield from
8. Yury Selivanov – @1st1 Coroutines: yield from & refactoring
9. Yury Selivanov – @1st1 Coroutines: async/await
10. Yury Selivanov – @1st1 • Dedicated syntax; concise and readable. • New builtin type for coroutines. • New concepts: async for and async with. • Generic, framework agnostic design. • Fast: only ~2x slower than a function call.
 10-100x faster than yield coroutines. Why async/await is the answer
11. Yury Selivanov – @1st1 async/await • Subtype of generators; shares a lot of code. • await —> yield from —> YIELD_FROM opcode. • @types.coroutine. • __await__. • __aenter__, __aexit__, __aiter__, __anext__.
12. Yury Selivanov – @1st1 async/await in real life: github.com/magicstack/asyncpg
13. Let’s talk about asyncio
14. Yury Selivanov – @1st1 asyncio • Developed and actively maintained by the BDFL. • A toolbox for frameworks and protocols. • Part of Standard Library. • Twisted (soon) and Tornado (now) can interoperate.
15. Yury Selivanov – @1st1 asyncio: what’s inside? • Standardized pluggable event loop. • Interfaces for Protocols and Transports. • Factories for servers and connections; streams. • Futures and Tasks: callbacks + coroutines, timeouts, cancellation, etc. • Subprocess, queues, synchronisation primitives.
16. Yury Selivanov – @1st1 asyncio is simple!
17. Yury Selivanov – @1st1 asyncio is simple. • asyncio.get_event_loop() • loop.create_task(). • loop.run_until_complete() and loop.run_forever(). • asyncio.gather(). • loop.run_in_executor(). • loop.close().
18. Yury Selivanov – @1st1 loop.create_task() Wraps coroutines in a “coroutine runner”: a mechanism for the 
 event loop to work with 
 async/await.
19. Yury Selivanov – @1st1 asyncio.gather() Awaits on multiple
 coroutines (or tasks, or futures.)
20. Yury Selivanov – @1st1 loop.run_in_executor() Runs slow 
 CPU-intensive or blocking IO code in a thread
 or in a process pool.
21. Yury Selivanov – @1st1 loop.close() Shuts down the 
 event loop and frees
 resources.
22. Yury Selivanov – @1st1 asyncio: debugging • PYTHONASYNCIODEBUG=1 python program.py
 or loop.set_debug().
 • Configure python logging to see errors. • Configure your test runner to print out warnings.
23. Let’s talk about uvloop
24. Yury Selivanov – @1st1 github.com/magicstack/uvloop • 99.(9)% compatible asyncio event loop. • Written in Cython. • Uses libuv under the hood. • Fast Tasks and Futures = faster async/await. • Super fast IO.
25. Yury Selivanov – @1st1 How fast is uvloop? 2-4x faster than asyncio.
26. Yury Selivanov – @1st1 OK, it’s faster than asyncio…
27. Yury Selivanov – @1st1 PEP 492
28. Yury Selivanov – @1st1 Language Summit 2015 • First time discussed the idea with Guido. • Two months before feature freeze. • He liked it!
29. Yury Selivanov – @1st1 PEP & Implementation • 2-5 days for the first draft of the PEP. • 40 hours to prototype in CPython. • 5 iterations of the PEP. • ~500 emails on python-ideas and python-dev. • Nick Coghlan and Victor Stinner reviewed the patch.
31. That’s it. Thank you. Questions?