import asyncio

Brněnské Pyvi, 2014-01-30

Transcript

1. import asyncio
   Petr Viktorin
   encukou@gmail.com
   Pyvo, 2014-01-30
   

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2. The problem
   Do something useful
   while waiting
   

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3. The problem
   Do something useful
   while waiting
   (for IO)
   

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4. The problems
   Do something useful
   while waiting
   (for IO)
   Do several things
   at the same time
   

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5. Multiple processes
   import subprocess
   

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6. Threads
   import threading
   

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7. Greenlets
   Event loop
   Cooperative multitacking
   Monkeypatching
   pip install eventlet gevent
   

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8. Callbacks
   Explicit cooperative
   multitasking
   pip install twisted
   

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9. Help! Which do I use?
   

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10. Compare: web frameworks
    

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11. Compare: web frameworks
    Flask app
    

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12. Compare: web frameworks
    Flask app
    Pyramid debug toolbar
    

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13. Compare: web frameworks
    Flask app
    Pyramid debug toolbar
    Cherrypy logging
    

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14. Compare: web frameworks
    Flask app
    Pyramid debug toolbar
    Cherrypy logging
    PEP 333 - Python Web Server
    Gateway Interface
    

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15. Let's do the same for async!
    

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16. Let's do the same for async!
    import asyncio
    

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17. Let's do the same for async!
    import asyncio
    Python 3.4+
    

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18. Let's do the same for async!
    import asyncio
    Python 3.4+
    pip install tulip
    

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19. Let's do the same for async!
    import asyncio
    Python 3.4+
    pip install tulip
    Python 3.3+
    

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20. asyncio
    Explicit cooperative
    multitasking
    

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21. asyncio
    Explicit cooperative
    multitasking
    like Twisted
    

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22. Global event loop
    

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23. Global event loop
    Event loop policy
    

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24. Callbacks
    

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25. Callbacks
    call_soon(callback, args)
    

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26. Callbacks
    call_soon(callback, args)
    call_later(delay, cb, *args)
    

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27. Callbacks
    call_soon(callback, args)
    call_later(delay, cb, *args)
    What is time?
    

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28. Callback style
    import asyncio
    def print_and_repeat(loop):
    print('Hello World')
    loop.call_later(2, print_and_repeat, loop)
    loop = asyncio.get_event_loop()
    loop.call_soon(print_and_repeat, loop)
    loop.run_forever()
    

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29. Futures
    

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30. Futures
    Placeholders for a result
    

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31. Futures
    Placeholders for a result
    future.result()
    

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32. Futures
    Placeholders for a result
    future.result()
    future.set_result()
    

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33. Futures
    Placeholders for a result
    future.result()
    future.set_result()
    future.set_exception()
    

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34. Futures
    Placeholders for a result
    future.result()
    future.set_result()
    future.set_exception()
    future.add_done_callback()
    

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35. Futures
    Placeholders for a result
    future.result()
    future.set_result()
    future.set_exception()
    future.add_done_callback()
    concurrent.futures
    

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36. Locks, Semaphores, Queues
    

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37. Locks, Semaphores, Queues
    http://xkcd.com/927/
    

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38. Couroutines & Tasks
    import asyncio
    @asyncio.coroutine
    def greet_every_two_seconds():
    while True:
    print('Hello World')
    yield from asyncio.sleep(1)
    print('How are you?')
    yield from asyncio.sleep(1)
    loop = asyncio.get_event_loop()
    loop.run_until_complete(greet_every_two_seconds())
    

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39. Transports & Protocols
    Transport: TCP, UDP, SSL
    Protocol: HTTP, FTP, IRC
    

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40. Echo client
    import asyncio
    class EchoClient(asyncio.Protocol):
    message = 'This is the message. It will be echoed.'
    def connection_made(self, transport):
    transport.write(self.message.encode())
    print('data sent: {}'.format(self.message))
    def data_received(self, data):
    print('data received: {}'.format(data.decode()))
    def connection_lost(self, exc):
    print('server closed the connection')
    asyncio.get_event_loop().stop()
    loop = asyncio.get_event_loop()
    coro = loop.create_connection(EchoClient, '127.0.0.1', 8888)
    loop.run_until_complete(coro)
    loop.run_forever()
    loop.close()
    

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41. Echo server
    import asyncio
    class EchoServer(asyncio.Protocol):
    def connection_made(self, transport):
    peername = transport.get_extra_info('peername')
    print('connection from {}'.format(peername))
    self.transport = transport
    def data_received(self, data):
    print('data received: {}'.format(data.decode()))
    self.transport.write(data)
    # close the socket
    self.transport.close()
    loop = asyncio.get_event_loop()
    coro = loop.create_server(EchoServer, '127.0.0.1', 8888)
    server = loop.run_until_complete(coro)
    print('serving on {}'.format(server.sockets[0].getsockname()))
    try:
    loop.run_forever()
    except KeyboardInterrupt:
    print("exit")
    finally:
    server.close()
    loop.close()
    

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42. ?
    Petr Viktorin
    @encukou.cz
    @encukou
    encukou@gmail.com
    github.com/encukou
    Slides available under the
    Creative Commons Attribution-ShareAlike 3.0
    http://creativecommons.org/licenses/by-sa/3.0/
    

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43. Sources & links
    PEP 3156 - Asynchronous IO Support Rebooted: the "asyncio"
    Module
    PEP 3148 - futures - execute computations asynchronously
    PEP 3153 (Superseded) - Asynchronous IO support
    http://docs.python.org/3.4/library/asyncio.html
    Youtube: Guido van Rossum - Tulip: Async I/O for Python 3
    

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