[Twisted-Python] how to get an idle callback while running a reactor?
joe at strout.net
Sat Dec 20 10:28:20 EST 2008
Jean-Paul Calderone wrote:
>> So I'm at a loss as to how to add an "idle" function that will allow
>> my bot to periodically see whether it has something new to say to the
> While this sometimes makes sense, it's usually *not* the approach you want
> to take. You're describing a solution which is essentially polling. And
> polling is not as good as responding to events. You *could* run a function
> ten times a second that looks around for a message to send and sends it if
> it finds one. Or, whatever event occurs which creates those messages could
> just send the message instead of putting it in a pile and waiting for your
> poller to find it.
Well, the thing is that there will actually be a great many things that
could cause it to need to send a message, such as the time, a change in
the outside temperature, a certain change in the value of a stock fund,
etc. And the AIM interface isn't the only interface to this bot. So I
really do think I need a way to call a function once every few seconds.
Now, that does suggest an alternative approach, which is to ignore
twisted's event/idle mechanisms and use something external to it. But
I'm also fairly newish to Python, so I'm not sure exactly how to do that
either -- reactor.run() is a blocking call, so I supposed I'd have to
use threads. Then my "idler thread" could call the idle function, sleep
for a few seconds, and repeat.
But if there's a simple way to do this within Twisted, I'd like to learn
what that is
>> Now, from trawling the docs, I guess that I want to call
> Probably not. If you want to run a function later (and that's how polling
> is generally implemented), you want reactor.callLater. If you want to run
> a function repeatedly at a fixed interval,
> twisted.internet.task.LoopingCall will help.
Thanks, I'll look at these.
> You'll probably encounter the same problem with reactor.callLater as you
> were encountering with reactor.callWhenRunning, though. How do you get
> a reference to the bound method to pass in? That's simple - don't call
> the reactor method until you *have* an instance. You can call almost any
> reactor method even *after* the reactor is started; you do not have to set
> everything up before you call reactor.run.
OK, so somewhere within my B class, maybe in initDone, set it up there?
That makes sense.
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