Wraps a function in a process that terminates after s seconds. returns None if process terminates else returns result.

maxtime_process.py

"""
Inspired from [1] and [2], but neither fit my need.  

The following lets you decorate a function with a time limit, kills it when it doesn't finish in that time.
The needed part for me was that I had to get the result if it didn't get killed and None if it did.

The following accomplished this.

[1] http://stackoverflow.com/a/26664130
[2] https://gist.github.com/aaronchall/6331661fe0185c30a0b4
"""


from __future__ import print_function
import sys
import threading
from time import sleep
import multiprocessing

def exit_after(s):
    '''
    use as decorator to exit process if
    function takes longer than s seconds
    '''
    def outer(fn):
        q = multiprocessing.Queue()

        def surrogate(*args, **kwargs):
            r = fn(*args, **kwargs)
            q.put(r)

        def inner(*args, **kwargs):
            p = multiprocessing.Process(target=surrogate, args=args, kwargs=kwargs)
            p.start()
            p.join(s)
            if p.is_alive():
                p.terminate()
                return None
            return q.get(False)
        return inner
    return outer

@exit_after(1)
def bad_func():
    print("Starting bad_func")
    sleep(5)
    print("Ending bad_func")
    return 5

@exit_after(1)
def good_func():
    print("good func")
    return 2

def test():
    print("starting test")
    r = bad_func()
    print("bad_func returned; result should be None. it =", r)
    r = good_func()
    print("good func returned. it should equal 2. it =", r)
    print("ending test")


if __name__ == "__main__":
    test()