I would like to set an alarm (similar to signal.alarm) where the granularity is finer than integer seconds. For example, I'd like to set an alarm for 0.4 seconds or 3.2 seconds. I'm particularly interested in alarms that last for less than one second.
In Python 3, I have only tried "import signal" and calling "signal.alarm(time)" where "time" is an integer. If "time" is a floating point number, the call fails. This is not surprising because the documentation says "time" must be an integer.
At one point in Python 2, I found some code that implemented access to "ualarm()" from Python but all of this is quite obsolete at this point.
You can use signal.setitimer for that:
signal.setitimer(signal.ITIMER_REAL, 0.5)
Of course, there are also all sorts of higher-level ways to arrange to do something 0.5 seconds from now, so going through low-level signal APIs may not be the best approach for what you're doing.
Also, keep in mind that the C sleep and usleep functions may be implemented using SIGALRM, so it's not safe to mix calls to signal.setitimer or signal.alarm with anything that might call C sleep or usleep. (Python's time.sleep doesn't use those functions, so it's probably fine.)