cross platform alternative for signal.SIGALRM?

[Terry Reedy]

On 11/11/2015 11:16 AM, Ulli Horlacher wrote:
> I am rewriting a Perl program into Python (2.7).

I recommend using 3.4+ if you possibly can.

> It must run on Linux and Windows.
> With Linux I have no problems, but Windows... :-(
>
> The current show stopper is signal.SIGALRM which is not available on
> Windows:

> Perl for Windows has had SIGALRM support (or some kind of emulation).
>
> Ok, I have to redesign this part of my code:
>
>    def timeout_handler(sig,frame):
>      raise ValueError("timeout!")
>
>    signal.signal(signal.SIGALRM,timeout_handler)
>
>    while True:
>      chunk = fileo.read(bs)
>      sock.sendall(chunk)
>      (...)
>
> What is the best practise for a cross platform timeout handler?

The cross-platform 3.4 asyncio module has some functions with timeouts.
(3.5 has new 'async' syntac which supposedly makes it easier to use.  I 
have not looked at this yet.)

For instance: coroutine asyncio.wait(futures, *, loop=None, 
timeout=None, return_when=ALL_COMPLETED)
     Wait for the Futures and coroutine objects given by the sequence 
futures to complete. Coroutines will be wrapped in Tasks. Returns two 
sets of Future: (done, pending).
...
Usage:
   done, pending = yield from asyncio.wait(fs)

I believe the backport on pypi.python.org, called tulip, works on 2.7.

In the example above, the read/send would be a task.  Wait on the task, 
and when it returns, cancel the task if in pending.


-- 
Terry Jan Reedy