[farshizzo]

I would highly recommend using the viztask module to control the flow of your program. Each stage would be implemented as a task and the main function would just yield each stage one after the other:

def stage1():
    while SomeCondition:
        
        #Do something each frame here

        #Wait for next frame
        yield None

def stage2():
    while SomeCondition:
        
        #Do something each frame here

        #Wait for next frame
        yield None

def main():
    #Execute stage 1 and wait for it to finish
    yield stage1()
    #Execute stage 2 and wait for it to finish
    yield stage2()

viztask.schedule(main())

There are a lot of examples in the docs showing how to use the viztask module. You can also ask here on the forum if you have more specific questions about it.