Is there a better way to implement this:

[Michael Yanowitz]

Hello:

I wrote the code below (much irrelevant code removed).
This doesn't quite work. What I wanted it to do was
a) Execute function ftimed, which takes a function and a timeout
in seconds.
b) This will also execute function abort() as a thread.
This function just runs for the specified
number of seconds and returns.
However, before it returns, throws an exception.
c) If test() is still running when abort() is
finished, ftimed() should catch the exception and
return.

It is catching the exception, however it continues running the function.
Why does it continue and not return?

What am I missing, or is there a better way to
implement this (having ftimed() return when the
abort-timer time is exceeded?


import time, thread, sys

thread_finished = "MAX RUN TIME EXCEEDED!"

def abort (seconds):
start_time = time.time()
while ((time.time() - start_time) < seconds):
time.sleep(0.01)
print "script run time exceeded max_run_time of", seconds, "seconds."
raise thread_finished
return


def test():
i = 0
while (True):
time.sleep(1)
print "HELLO", i
i+=1


def ftimed (func, seconds):
thread.start_new_thread (abort, (seconds,))

try:
func()
except thread_finished:
print "Timeout"
return

ftimed (test, 30)
print "Script finished"

It presently generates the following output:
$ python ./testthread.py
HELLO 0
HELLO 1
HELLO 2
HELLO 3
HELLO 4
HELLO 5
HELLO 6
HELLO 7
HELLO 8
HELLO 9
HELLO 10
HELLO 11
HELLO 12
HELLO 13
HELLO 14
HELLO 15
HELLO 16
HELLO 17
HELLO 18
HELLO 19
HELLO 20
HELLO 21
HELLO 22
HELLO 23
HELLO 24
HELLO 25
HELLO 26
HELLO 27
HELLO 28
HELLO 29
script run time exceeded max_run_time of 30 seconds.
Unhandled exception in thread started by <function abort at 0x009CEF30>
Traceback (most recent call last):
File "./testthread.py", line 10, in abort
raise thread_finished
MAX RUN TIME EXCEEDED!
HELLO 30
HELLO 31
HELLO 32
.....



Thanks in advance:
Michael Yanowitz

 

[Benjamin Niemann]

Hello:

I wrote the code below (much irrelevant code removed).
This doesn't quite work. What I wanted it to do was
a) Execute function ftimed, which takes a function and a timeout
in seconds.
b) This will also execute function abort() as a thread.
This function just runs for the specified
number of seconds and returns.
However, before it returns, throws an exception.
c) If test() is still running when abort() is
finished, ftimed() should catch the exception and
return.

It is catching the exception, however it continues running the function.
Why does it continue and not return?

The exception is raised in the thread that executes the abort() function.
The exception does not get caught and terminates this thread. The other
(main) thread is unaffected - exceptions are local to a thread and there is
currently no (portable) way to raise an exception in another thread.

What am I missing, or is there a better way to
implement this (having ftimed() return when the
abort-timer time is exceeded?

You may use the signal.alarm() function, if you are on a UNIXoid system and
you have only a signle time-out at a time (e.g. not nested).

import time, thread, sys

thread_finished = "MAX RUN TIME EXCEEDED!"

def abort (seconds):
start_time = time.time()
while ((time.time() - start_time) < seconds):
time.sleep(0.01)

any reason for not using time.sleep(seconds) here?

 

[Paul Boddie]

I guess I am looking for something portable (both
Windows and Linux) where I can abort a function after
a certain time limit expires.

Doing a search for "timeout function Python" on Google reveals a number
of approaches.

Using signals:

* http://nick.vargish.org/clues/python-tricks.html
* http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/307871

Using threads:

* http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/473878

Using processes:

* http://lfw.org/python/delegate.html

Paul

 

[Peter Otten]

Doing a search for "timeout function Python" on Google reveals a number
of approaches.

Using threads:

* http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/473878

That doesn't abort the calculation, however -- it just moves on with a
default value instead of the actual result if that is not available after
the specified timespan.

The calculation may go on forever eating up resources.

Peter