Python good process kill

good_process_kill.py

def _process_kill(pid, signal=0):
    """Send a signal to a process.

    :Returns:
    ----------
    True if the pid is dead
    with no signal argument, sends no signal.
    """
    # if 'ps --no-headers' returns no lines, the pid is dead
    from os import kill
    try:
        return kill(pid, signal)
    except OSError as e:
        # process is dead
        if e.errno == 3:
            return True
        # no permissions
        elif e.errno == 1:
            return False
        else:
            raise e


def _process_dead(pid):
    if _process_kill(pid):
        return True
    # maybe the pid is a zombie that needs us to wait4 it
    from os import waitpid, WNOHANG
    try:
        dead = waitpid(pid, WNOHANG)[0]
    except OSError as e:
        # pid is not a child
        if e.errno == 10:
            log.warning("Process PID %s not a child. Can't kill it." % pid)
            return False
        else:
            raise e
    return dead

# def kill(pid, sig=0): pass #DEBUG: test hang condition


def process_goodkill(pid, interval=1, hung=20):
    """Let process die gracefully.

    Gradually send harsher signals
    if necessary.

    :Returns:
    ---------
    True if the process was killed and exited cleanly.
    False if the process kill hung up and couldn't be cleaned.
    """
    from signal import SIGTERM, SIGINT, SIGHUP, SIGKILL
    from time import sleep

    for signal in [SIGTERM, SIGINT, SIGHUP]:
        if _process_kill(pid, signal):
            return
        if _process_dead(pid):
            return
        sleep(interval)

    i = 0
    while True:
        # infinite-loop protection
        if i < hung:
            i += 1
        else:
            log.warning("Process PID %s is hung. Giving up kill." % pid)
            return
        if _process_kill(pid, SIGKILL):
            return
        if _process_dead(pid):
            return
        sleep(interval)