Example of a pseudo-timeout implementation for short, recursive calls

pseudo-timeout example

import time

def timer(timeout):
    """Creates a timer callback function. Function will return True if
    the time is up, otherwise returns False."""

    TIME = time.time() + timeout
    def callback():
        if time.time() > TIME:
            return True
        else:
            return False
    return callback

def testrecur(n, tcb=None):
    """The recursive function. Checks for timeout first. If not timed out,
    computes the function result, otherwise raises a TimeoutError."""

    # Boilerplate check for timeout
    if not tcb or not tcb():
        # This is the actual function block
        if n:
            time.sleep(1)
            return n + testrecur(n - 1, tcb)
        else:
            return 0
    # More boilerplate - returning error if timedout
    else:
        raise TimeoutError()


def test(n, timeout=None):
    """The entry point for this function. Creates a timeout callback, calls the
    recursive function. If timeout, just returns the argument, otherwise return
    the result."""

    # Create the timeout callback
    if timeout:
        tcb = timer(timeout)
    else:
        tcb = lambda: False

    # Call the recursive function. IF it times out, return the argument instead
    try:
        return testrecur(n, tcb=tcb)
    except TimeoutError:
        return n

if __name__ == '__main__':
    # This will return in 5 seconds
    print(test(5))
    # We can force it to return in ~2 seconds with a timeout
    print(test(5, 2))