Real-time interrupts in Python

Question

I have a Python 2.7 program running an infinite while loop and I want to incorporate a timer interrupt. What I aim to do is to set off a timer at some point in the loop, and

Answer 1

You can't get real-time without special hardware/software support. You don't need it in most cases (do you need to control giant robots?).

How to delay several function calls by known numbers of seconds depends on your needs e.g., if a time it takes to run a function is negligible compared to the delay between the calls then you could run all functions in a single thread:

#!/usr/bin/env python
from __future__ import print_function
from Tkinter import Tk

root = Tk()
root.withdraw() # don't show the GUI window
root.after(1000, print, 'foo') # print foo in a second
root.after(0, print, 'bar') # print bar in a jiffy
root.after(2000, root.destroy) # exit mainloop in 2 seconds
root.mainloop()
print("done")

It implements yours "I do not want the interrupts to interrupt each other either" because the next callback is not called until the previous one is complete.

Answer 2

If a single event is to be handled, then the easiest way is to use the signal framework which is a standard module of Python.

However, if we need a fully-fledged scheduler, then we have to resort to another module: sched. Here is a pointer to the official documentation. Please be aware, though, that in multi-threaded environments sched has limitations with respect to thread-safety.

Another option is the Advanced Python Scheduler, which is not part of the standard distribution.