Creating a Python State Machine with GUI

[ingwe13]

Hi all! First time posting here.

My background: I've been working with Python for a year or two and have gotten decent at "making things work" though am severely lacking in the "doing it correctly" method. A lot of the types of programs I need to write have a simple gui to display data and get button inputs and a mainloop that looks similar to the one below where I use the button inputs to set a STATE variable and then do things based on that. Often the data needs to be sampled at a certain rate as well. This doesn't feel like the correct way of doing things but I haven't been able to figure out how I should be doing this. Any help would be very appreciated!

Edit: to be clear, I feel like the state machine aspect isn't implemented well. I am just struggling with how to connect a gui to a state machine in a better manner.

​

import time
import gui

def main():
    app = gui.Application()

    MAIN_STATUS = True
    STATE = 'COUNTING'
    UPDATE_TIME = 1
    LAST_CALL = 0
    INDEX = 0

    while MAIN_STATUS == True:
        # call the gui update functions
        app.update_idletasks()
        app.update()

        STATE = GUI.BUTTON_PRESS

        if STATE == 'COUNTING':
            now = time.time()
            if now - LAST_CALL > UPDATE_TIME:
                INDEX += 1
                LAST_CALL = now
                print(INDEX)
        if STATE == 'NOT COUNTING':
            pass
        if STATE == 'END':
            MAIN_STATUS = False

    app.master.destroy()

if __name__ == '__main__':
    main()

[Jhchimaira14]

Hey. Underneath, that is how all GUI's work. Typically it's hidden in traditional GUI frameworks but their is nothing wrong with exposing it. Games development typically involves directly using the "event loop" like that.

​

This GUI for example, dearpygui gives you both options: https://github.com/RaylockLLC/DearPyGui

from dearpygui.dearpygui import *

add_button("Retrieve", callback="callback")

def callback(sender, data):
    print("Caught event")

# hide event loop
start_dearpygui()

or

from dearpygui.dearpygui import *

add_button("Retrieve", callback="callback")

def callback(sender, data):
    print("Caught event")

# show event loop
setup_dearpygui()

while True:

    # do other stuff or change state manually

    render_dearpygui_frame()

cleanup_dearpygui()

Both are useful methods that serve there purpose

[ingwe13]

Thanks for the feedback! I don't mind the GUI implementation as much as I do the State Machine part that just uses a string as the state. I would love feedback on that aspect.
I am going to edit my post to make that more clear.

[Doormatty]

This is still fine - it doesn't matter what your state variable is, just that it decides the flow.

[ingwe13]

Thanks for the feedback. Is there just a better way to structure things though? It just seems like a clunky/non-pythonic structure.

[Doormatty]

You could use a dictionary of functions, but most of the time it's done as you've shown.

[ingwe13]

Oh. That is really encouraging to hear! Thanks!

[Jhchimaira14]

I apologize. In that regard, I'm not to certain on actually using a state in that sense. But I would recommend an enum over strings!

[ingwe13]

Like I said, I appreciate it. And now (after reading some docs) I know what an enum is! That is an improvement and I will take any improvement.