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Jyrki Pulliainen / 18.10.2011
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Going concurrent
asynchronous with Python
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Motivation
• Not threaded
• Good for I/O bound software
• Buzzword-compatible!
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Two ways to achieve
• Coroutines
• Event loop
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Coroutines
• Components, that are suspendable / resumable
• One scheduler to rule them all
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Coroutines in Python
• Python 2.5 added support for coroutines
>>>def coroutine():
>>> input = yield i
>>> print i + 1
>>> a = coroutine()
>>> a.next()
>>> a.send(1)
2
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Running multiple coroutines
def main_loop(self):
while self.tasks_left():
task = self.get_next_task()
try:
task.send(None)
except StopIteration:
# Do not schedule if the task is done
self.remove_task(task)
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Event loop
• Good for I/O
• Main idea: Wait for something to happen, then pass to a handler
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Idea in a nutshell
class EventLoop(object):
# ...
def main_loop():
while True:
event = self.wait_for_event()
handler = self.get_handler_for_event(handler)
handler()
Wednesday, October 19, 2011
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Going asynchronous with Python
/ Finding events
• Usually you want to poll I/O
• Tools for that: select, kselect, epoll...
Wednesday, October 19, 2011
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Jyrki Pulliainen / 18.10.2011
/
CODE TIEM!!11
(actually, just looking at it)
Wednesday, October 19, 2011