tk_greenlet_demo.py

import tkinter as tk
import greenlet
from random import randint, choice

MAX_X, MAX_Y = 800, 600

def scheduler(tasks, max_ticks=None):
    tasks = list(tasks)

    def scheduler_task(parent_tick=None):
        parent = greenlet.getcurrent().parent

        tick = 0
        while tasks and (max_ticks and tick < max_ticks if max_ticks else True):
            parent.switch()

            for t in tasks[:]:
                t.switch(tick)
                if t.dead:
                    tasks.remove(t)

            tick += 1

    sched = greenlet.greenlet(scheduler_task)
    for t in tasks:
        t.parent = sched

    return sched


def circle_task(canvas):
    def task(tick):
        parent = greenlet.getcurrent().parent

        x = randint(0, MAX_X - 10)
        y = randint(0, MAX_Y - 10)
        color = choice(["red", "green", "blue", "purple"])
        dx, dy = choice([(1, 1), (-1, 1), (-1, -1), (1, -1)])
        dx *= randint(5, 20)
        dy *= randint(5, 20)

        shape_id = canvas.create_oval(x, y, x + 10, y + 10, fill=color)

        while True:
            try:
                parent.switch()
            except greenlet.GreenletExit:
                canvas.delete(shape_id)
                break

            new_x = x + dx
            new_y = y + dy
            if MAX_X < new_x or new_x < 0:
                dx = -dx
            if MAX_Y < new_y or new_y < 0:
                dy = -dy
            x = new_x
            y = new_y
            canvas.move(shape_id, dx, dy)

    return greenlet.greenlet(task)


def update_task(canvas):
    def task(tick):
        parent = greenlet.getcurrent().parent
        while True:
            parent.switch()
            canvas.update()
    return greenlet.greenlet(task)


if __name__ == '__main__':
    import sys
    num_of_shapes = int((sys.argv[1:] or ["5"])[0])

    root = tk.Tk()
    frame = tk.Frame(root)
    frame.pack()
    canvas = tk.Canvas(frame, width=MAX_X, height=MAX_Y, bg="black")
    canvas.pack()

    sched = scheduler(
        [circle_task(canvas) for _ in range(num_of_shapes)] +
        [update_task(canvas)]
    )
    def update():
        if not sched.dead:
            sched.switch()
            root.after(50, update)
    update()

    def key_handler(event):
        if event.keysym == 'Escape':
            sched.throw(greenlet.GreenletExit)
            root.quit()

    root.bind_all('<Key>', key_handler)
    root.mainloop()