Python在例程之间切换

Question

I am writing a python program where I have three routines that need to switch between each other including a main loop, set up as follows:

pseudo-code:

main routine: 
   run routine, 
   while running:
    if obtained signal A run routine A, 
    else if obtained signal B run routine B

routine A: 
  run routine, 
  while running:
  if obtain signal B, run routine B, 
   else if completed with no signal run main
  else if no signal, just keep running

routine B: 
  run routine, 
  while running
  if obtain signal A, run routine A, 
  else if completed with no signal run main.

Where signal could sent by a handler that sets a variable that has an associated Lock on it. No two routines need to run simultaneously.

I was thinking of using non-preemptive threads, and wondering if there exists a way to do non-preemptive threading python where threads can specifically yield to another target thread? I found Yarn , but I don't know if that solves the problem. In addition, I was wondering if there is better way to accomplish this, maybe using co-routines instead?

Answer 1

Something like that?

from random import choice

get_signal_somehow = lambda: choice(["A", "B"])

def main():
    A = routine_a()
    B = routine_b()
    signal = get_signal_somehow()
    while True:
        if signal == 'A':
            signal = next(A)
        elif signal == 'B':
            signal = next(B)

def routine_a():
    #do stuff
    if get_signal_somehow() == 'B':
        yield 'B'
    else:
        yield 'A'

def routine_b():
    #do stuff
    if get_signal_somehow() == 'A':
        yield 'A'
    else:
        yield 'B'