The document is a presentation on Stackless Python, which extends Python with lightweight threading and tasklets. It discusses how Stackless provides more readable asynchronous code through tasklets and channels instead of callbacks. Examples show how tasklets can block and communicate without blocking the scheduler, allowing cooperative multitasking.

1. Stackless Python 101 An advanced level presentation in 20 minutes Kiwi PyCon 9 th November 2009 Richard Tew [email_address] www.stackless.com

2. What is Stackless? An extended version of Python.

3. Backwards compatible.

4. Stable.

5. Who uses Stackless CCP Games

6. Who the hell knows?

7. What Stackless provides Lightweight threading.

8. More readable code.

9. Persistence of running code.

10. Lightweight threading?

11. The shared thread

12. More readable code def Function_1(): Function_2() def Function_2(): Current_Function() def Current_Function(): # whatever...

13. Reasons to block Allow other tasklets to run.

14. Reawaken when event occurs.

15. Reawaken when time has passed.

16. Example: Python sockets def Function_1(self): self.socket = socket(AF_INET, SOCK_STREAM) ... self.Function_2() def Blocking_Function(self): return self.socket.recv(1000)

17. stacklesssocket.py Third party library. Monkey patches in place of Python sockets import stacklesssocket stacklesssocket.install()

18. Example: Stackless sockets def Function_1(self): self.socket = socket(AF_INET, SOCK_STREAM) ... self.Function_2() def Blocking_Function(self): return self.socket.recv(1000)

19. Where's the readability? No callbacks. No boilerplate. Just a function call. do_something_i_dont_care_if_you_block()

20. Comparison: generators Generators block to the calling function. Not the scheduler. http://www.dabeaz.com/coroutines

21. Using Stackless Tasklets.

22. The scheduler.

23. Channels.

24. The scheduler stackless.run(...)

25. Scheduling cooperatively Tasklets choose when to block stackless.schedule() channels... Run the scheduler until it is empty. stackless.run()

26. Scheduling preemptively while 1: interruptedTasklet = stackless.run(100) interruptedTasklet.insert() # Do other stuff.

27. Tasklets stackless.tasklet(print_args)(1, 2, x=“test“)

28. Tasklets and threads

29. Tasklet yielding def print_args(*args, **kwargs): while 1: print 'args', args print 'kwargs', kwargs stackless.schedule()