Python中的实时中断

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.

Answer 2

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 eg, 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.