how do you implement a reactor without a select?

[Michele Simionato]

On May 7, 7:36 pm, "sjdevn... at yahoo.com" <sjdevn... at yahoo.com> wrote:
>
> Busy-looping like that is ugly and inefficient, even with the sleep
> thrown in.
>
> Most GUI main loops _do_ use either select() or poll().  When Xt/GTK/
> Qt/etc have function like "gtk_add_input" which takes an fd that
> you'll get notified about if it's written to while you're in the main
> loop, that's just adding another fd to the select() loop.
>
> There are other ways to wait for events on an fd, but they tend to be
> less portable.  Depending on your Unix flavor, epoll, /dev/poll,
> kqueues, kevent, queued realtime signals, or something else might be
> available from the OS (but probably not from Python without futzing
> with ctypes or writing an extension).  If you want details, check outhttp://www.kegel.com/c10k.html
>
> The alternatives usually aren't really faster unless you have hundreds
> of connections, though--select/poll have major portability advantages,
> so go with them unless you have a compelling reason.

I see where you are coming from. In a GUI or in a Web server most
of the time is spent waiting from input, so a busy loop design would
be a terrible
design indeed. But I had another use case in mind. The code I posted
is
extracted from a batch script I have, called 'dbexplorer'. The script
performs lots of
queries in a database and find out "bad" data according to some
criterium.
So at each iteration there is a default action which is nontrivial; it
becomes
a time.sleep only at the end, when the batch has finished its job and
it
is waiting for input.In normal conditions most of the time is spent
doing
something, not waiting, so the busy loop design here is not so bad.
Still I wanted to know what my alternatives were. And from this thread
I gather the impression that actually the only portable alternative is
using some
kind of select, unless I want to use threads, and in that case the
scheduler approach could be viable.
Anyway, that  C10K page is really an interesting resource, thanks for
pointing it out!

               Michele Simionato