Palestra ministrada no TDC 2016 sobre como dar os primeiros passos com o módulo AsyncIO do Python.

1. pen4education
Seu Primeiro Loop com AsyncIO
Carlos Maniero
Desenvolvedor Python na Loja Integrada

2. pen4education
Não tenha medo

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Motivacional
“É necessário a disciplina de um super humano
para escrever código legível baseado em
callbacks, se você não acredita em mim, olhe
qualquer pedaço de código javascript.”

4. pen4education
Motivacional
“É necessário a disciplina de um super humano
para escrever código legível baseado em
callbacks, se você não acredita em mim, olhe
qualquer pedaço de código javascript.”
Guido Van Rossum

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Motivacional
https://www.python.org/~guido/

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Polêmica
“Threads em Python são
excelentes em fazer nada.”
David Beazley
http://www.dabeaz.com/

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Hello World
import asyncio
async def hello_world():
print("Hello World!")
loop = asyncio.get_event_loop()
loop.run_until_complete(hello_world())
loop.close()
Python 3.5

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Hello World
import asyncio
@asyncio.coroutine
def hello_world():
print("Hello World!")
loop = asyncio.get_event_loop()
loop.run_until_complete(hello_world())
loop.close()
Python 3.4

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Py 3.4 vs Py 3.5
Python 3.4 Python 3.5
async def hello_world():
@asyncio.coroutine
def hello_world():
await x()yield from x()

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Event Loop
O Event Loop é o dispositivo central de execução.
● Registra, executar e cancela tarefas
● Cria servidores e clients para vários tipos de
comunicação (ex: sockets)
● Delega processos pesados a um executor. (ex:
ThreadPoolExecutor)

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Coroutine
Coroutine utiliza do statement yield do Python para
controlar a execução do código de uma função.
Sendo possível bloquear, continuar e realizar a
comunicação sem a necessidade de criação de
funções de callback.

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0
n total
1 None

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0
n total
1 10

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0
n total
2 30

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0
n total
2 30

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Coroutine
def media():
n = 1
total = yield
while True:
total += (yield total / n)
n += 1
coro = media()
next(coro)
print(coro.send(10))
>>> 10.0
print(coro.send(20))
>>> 15.0
n total
2 30

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Task/Future
● Responsável pelo controle de execução de uma
corroutine.
● Contém importantes métodos como done(),
result() e cancel().
● Uma Task só é gerada pelo asyncio, utilizando
o asyncio.ensure_future() ou o loop.create_task
().

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import asyncio
async def loading():
i = 1
while True:
print('Loading ' + '.' * i)
await asyncio.sleep(0.5)
i += 1
async def run_very_long_task():
await asyncio.sleep(3)
return 42
async def supervisor():
loading_task = asyncio.ensure_future(loading()) # Cria task
content = await run_very_long_task() # Espera por retorno
loading_task.cancel() # Cancela execução da task
print('The result is {}'.format(content))
loop = asyncio.get_event_loop()
loop.run_until_complete(supervisor())
loop.close()
Task/Future

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import asyncio
async def loading():
i = 1
while True:
print('Loading ' + '.' * i)
await asyncio.sleep(0.5)
i += 1
async def run_very_long_task():
await asyncio.sleep(3)
return 42
async def supervisor():
loading_task = asyncio.ensure_future(loading()) # Cria task
content = await run_very_long_task() # Espera por retorno
loading_task.cancel() # Cancela execução da task
print('The result is {}'.format(content))
loop = asyncio.get_event_loop()
loop.run_until_complete(supervisor())
loop.close()
Task/Future
Loading .
Loading ..
Loading ...
Loading ....
Loading .....
Loading ......
The result is 42

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import asyncio
async def loading():
i = 1
while True:
print('Loading ' + '.' * i)
await asyncio.sleep(0.5)
i += 1
async def run_very_long_task():
await asyncio.sleep(3)
return 42
async def supervisor():
loading_task = asyncio.ensure_future(loading())
content = await run_very_long_task()
loading_task.cancel()
print('The result is {}'.format(content))
loop = asyncio.get_event_loop()
loop.run_until_complete(supervisor())
loop.close()

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import asyncio
async def loading():
i = 1
while True:
print('Loading ' + '.' * i)
await asyncio.sleep(0.5)
i += 1
async def run_very_long_task():
await asyncio.sleep(3)
return 42
async def supervisor():
loading_task = asyncio.ensure_future(loading())
content = await run_very_long_task()
loading_task.cancel()
print('The result is {}'.format(content))
loop = asyncio.get_event_loop()
loop.run_until_complete(supervisor())
loop.close()

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import asyncio
async def loading():
i = 1
while True:
print('Loading ' + '.' * i)
await asyncio.sleep(0.5)
i += 1
async def run_very_long_task():
await asyncio.sleep(3)
return 42
async def supervisor():
loading_task = asyncio.ensure_future(loading())
content = await run_very_long_task()
loading_task.cancel()
print('The result is {}'.format(content))
loop = asyncio.get_event_loop()
loop.run_until_complete(supervisor())
loop.close()

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import asyncio
import time
def slow_function():
time.sleep(3)
return 42
async def test1():
slow_function()
print('Finish test1')
async def test2():
for i in range(0, 10):
print(i)
await asyncio.sleep(0.5)
print('Finish test2')
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait([
test1(),
test2()
]))
Bloqueio do Loop
Finish test1
0
1
2
3
4
5
6
7
8
9
Finish test2

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import asyncio
import time
def slow_function():
time.sleep(3)
return 42
async def test1():
await loop.run_in_executor(None, slow_function)
print('Finish test1')
async def test2():
for i in range(0, 10):
print(i)
await asyncio.sleep(0.5)
print('Finish test2')
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait([
test1(),
test2()
]))
Bloqueio do Loop
0
1
2
3
4
5
Finish test1
6
7
8
9
Finish test2

27. pen4education
O que ver a seguir?
● ThreadPoolExecutor
● aioHTTP

28. pen4education
Obrigado <3
github.com/carlosmaniero
youtube.com/carlosmaniero
carlosmaniero@gmail.com