When I put a for loop into a tkinter project the shape doesn't show up

Question

I am making a random walk using Tkinter. For this to work I need to repeat the loop so I can change the way the dot is going move, because if I don't its just going to go one way. But when I put a "for loop" into the project the dot disappears.

import tkinter as tk
from tkinter import *
import random
# --- functions ---



def move_b():
    #calculating the way
    for x in range(10):
        x1_1 = 0
        y1_1 = 0

        #choosing to move x or y
        choose = random.randrange(0, 1)

        if choose == 0:
            #"ch" stands for change
            x_ch = random.randrange(0, 1)
            #if x_ch is 1 it moves right, if it is 0 it moves left
            if x_ch == 1:
                canvas.move(b, 1, 0)
            elif x_ch == 0:
                canvas.move(b, -1, 0)
        elif choose == 1:
            #"ch" stands for cange
            y_ch = random.randrange(0, 1)
             #if y_ch is 1 it moves up, if it is 0 it moves down
            if y_ch == 1:
                canvas.move(b, 0, 1)
            elif y_ch == 0:
                canvas.move(b, 0, -1)

    canvas.move(b, 1, 1)
    # move again after 25ms (0.025s)
    root.after(25, move_b)

# --- main ---

# init
root = tk.Tk()


# create canvas
canvas = tk.Canvas(root)
canvas.pack()
root.geometry("800x800")



# create objects
b = canvas.create_rectangle(40, 40, 40, 40, fill='black')



# start moving `b` automatically
move_b()

# start program
root.mainloop()