On Sat, Jun 20 2015, anu sree wrote: > Hi, > > I have seen an example of gevent context switch > http://sdiehl.github.io/gevent-tutorial/#synchronous-asynchronous-execution > > Could you please give some real use case with example. > It would be fine If you can share link of github project which uses gevent > context gevent.sleep(0).
[...] The difference between a regular sleep and a gevent sleep is that the gevent sleep will not make the whole interpreter process sleep. It will instead, only make the current greenlet sleep which essentially tells the internal scheduler to not execute it till the time is over. You can see this happen like this. Make a greenlet in your interpreter like so >>> from gevent import Greenlet >>> class Printer(Greenlet): ... def _run(self): ... n = 0 ... while True: ... n += 1 ... print n This simply prints numbers starting from 1. now you can create this greenlet and start it >>> p = Printer() >>> p.start() Nothing will happen. This is cooperative multitasking where the current Greenlet (your interpreter shell) has to "give up" its time slice and let p execute. You can do this by monkey patching sleep >>> from gevent import monkey >>> monkey.patch_time() >>> import time >>> time.sleep(1) Now, control is handed over to the Greenlet. However, it is not cooperative and runs a tight loop without ever giving up control. This means, that you'll never be able to execute your own interpreter again. So you see, the various greenlets have to "cooperate" to get things done. This is in counter distinction to how preemptive multitasking works where the OS can force the currently executing thread or process to stop and then grant execution to something else. They don't need to be nice. If your greenlet looked like this >>> class Printer(Greenlet): ... def _run(self): ... n = 0 ... while True: ... n += 1 ... time.sleep(0.1) ... print n the slot would be given up inside each iteration and other greenlets can execute. Try it. So people stick in a call to a monkey patched version of sleep inside tight loops to suspend the current interpreter for a short period of time thereby letting other greenlets execute. Krace's example is a good one. -- Cordially, Noufal http://nibrahim.net.in _______________________________________________ BangPypers mailing list BangPypers@python.org https://mail.python.org/mailman/listinfo/bangpypers
