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 when 5 seconds have elapsed I want the code to branch to a specific part of the while loop.

What I have been doing so far is the following: in each iteration of the while loop I am checking how much time has elapsed when I reach that point in the code using

time.clock()

and if the difference exceeds 5 I run the chunk of code I mean to run

However that way 7 seconds might pass before I evaluate the time, it will be >5sec but I want to go there exactly when 5 seconds pass

Also, I need this to work for more than 1 counter (possibly up to a 100) but I do not want the interrupts to interrupt each other. Using Timer did not work either.

I know this can be done using timer interrupts in assembly but how can I do that in python?

Answer 1

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.