Mutli-threading python with Tkinter

Question

I'm drawing little circles on a canvas with these functions :

This is the function that will draw the circles :

class Fourmis:

def __init__(self, can, posx, posy, name, radius):
    self.can = can

    self.largeur_can = int(self.can.cget("width"))
    self.hauteur_can = int(self.can.cget("height"))

    self.posx = posx
    self.posy = posy
    self.name = name 
    self.radius = radius

    self.ball1 = self.can.create_oval(self.posy, self.posx, self.posy+radius, self.posx+radius, outline=self.name, fill=self.name, width=2)

    self.nx = randrange(-10,10,1)
    self.nx /= 2.0
    self.ny = randrange(-10,10,1)
    self.ny /= 2.0

    #self.can.bind("<Motion>", self.destruction, add="+") 
    self.statut = True

    self.move()

def move(self):
    if self.statut == True :
        self.pos_ball = self.can.coords(self.ball1)
        self.posx_ball = self.pos_ball[0]
        self.posy_ball = self.pos_ball[1]

        if self.posx_ball < 0 or (self.posx_ball + self.radius) > self.largeur_can:
            self.nx = -self.nx         
        if self.posy_ball < 0 or (self.posy_ball + self.radius) > self.hauteur_can:
            self.ny = -self.ny

        self.can.move(self.ball1, self.nx, self.ny)

        self.can.after(10, self.move)

this one creates the canvas and the circles :

class App(Frame):

def __init__(self):
    self.root=Tk()
    self.can=Canvas(self.root,width=800,height=600,bg="black")
    self.can.pack()

    self.create(50, "green")
    self.create(50, "purple")



def mainloop(self):
    self.root.mainloop()


def create(self, i, name):
    for x in range(i):
        self.x=Fourmis(self.can,100,400, name,0)

I call these lines to run the project :

jeu = App()
jeu.mainloop()

What is the correct way to execute self.create(50, "green") and self.create(50, "purple") in different threads?

I have tried the following, but could not get it to work.:

class FuncThread(threading.Thread):
def __init__(self, i, name):
    self.i = i
    self.name = name
    threading.Thread.__init__(self)

def run(self):
    App.create(self, self.i, self.name)

Is someone able to tell me how to run these threads?

Answer 1

When this functionality is needed, what you do is schedule the events you wish to perform by putting them in a queue shared by the threads. This way, in a given thread you specify that you want to run "create(50, ...)" by queueing it, and the main thread dequeue the event and perform it.

Here is a basic example for creating moving balls in a second thread:

import threading
import Queue
import random
import math
import time
import Tkinter

random.seed(0)

class App:
    def __init__(self, queue, width=400, height=300):
        self.width, self.height = width, height
        self.canvas = Tkinter.Canvas(width=width, height=height, bg='black')
        self.canvas.pack(fill='none', expand=False)
        self._oid = []
        self.canvas.after(10, self.move)

        self.queue = queue
        self.canvas.after(50, self.check_queue)

    def check_queue(self):
        try:
            x, y, rad, outline = self.queue.get(block=False)
        except Queue.Empty:
            pass
        else:
            self.create_moving_ball(x, y, rad, outline)
        self.canvas.after(50, self.check_queue)

    def move(self):
        width, height = self.width, self.height
        for i, (oid, r, angle, speed, (x, y)) in enumerate(self._oid):
            sx, sy = speed
            dx = sx * math.cos(angle)
            dy = sy * math.sin(angle)
            if y + dy + r> height or y + dy - r < 0:
                sy = -sy
                self._oid[i][3] = (sx, sy)
            if x + dx + r > width or x + dx - r < 0:
                sx = -sx
                self._oid[i][3] = (sx, sy)
            nx, ny = x + dx, y + dy
            self._oid[i][-1] = (nx, ny)
            self.canvas.move(oid, dx, dy)
        self.canvas.update_idletasks()
        self.canvas.after(10, self.move)

    def create_moving_ball(self, x=100, y=100, rad=20, outline='white'):
        oid = self.canvas.create_oval(x - rad, y - rad, x + rad, y + rad,
                outline=outline)
        oid_angle = math.radians(random.randint(1, 360))
        oid_speed = random.randint(2, 5)
        self._oid.append([oid, rad, oid_angle, (oid_speed, oid_speed), (x, y)])

def queue_create(queue, running):
    while running:
        if random.random() < 1e-6:
            print "Create a new moving ball please"
            x, y = random.randint(100, 150), random.randint(100, 150)
            color = random.choice(['green', 'white', 'yellow', 'blue'])
            queue.put((x, y, random.randint(10, 30), color))
        time.sleep(0) # Effectively yield this thread.

root = Tkinter.Tk()
running = [True]

queue = Queue.Queue()

app = App(queue)
app.create_moving_ball()
app.canvas.bind('<Destroy>', lambda x: (running.pop(), x.widget.destroy()))

thread = threading.Thread(target=queue_create, args=(queue, running))
thread.start()

root.mainloop()