Initial Commit

When using tkinter in python, there seems to be some sutble conflict when using tk.update() and tk.mainloop() at the same time.

hanoi.py

@@ -0,0 +1,215 @@
+# -*- coding: utf-8 -*-
+"""
+Created on Sat Apr 25 21:18:50 2020
+
+@author: cpan
+"""
+
+import tkinter as tk
+import time
+
+gbl_num_disks = 3
+GAP = 2
+CANVAS_W = 500
+CANVAS_H = 400
+gbl_speed = 0.001 # in seconds
+gbl_pegs = []
+gbl_pegstate = [[], [], []]
+gbl_disks = []
+gbl_tkroot = tk.Tk()
+gbl_canvas = None
+gbl_ready = True
+
+
+def setup_gui():
+    global gbl_canvas
+
+    def get_ent(event):
+        global gbl_num_disks
+
+        try:
+            new_num = int(ent_disks.get())
+            gbl_num_disks = new_num
+            event.widget.tk_focusNext().focus()
+            draw_init_setting()
+        except Exception as err:
+            ent_disks.delete(0, tk.END)
+            ent_disks.insert(0, str(gbl_num_disks))
+            print(repr(err))
+        # print(gbl_num_disks)
+
+    # options row
+    tk_row = tk.Frame(gbl_tkroot)
+    tk.Label(tk_row, text="No. of Disks: ").pack(side=tk.LEFT)
+    ent_disks = tk.Entry(tk_row, width=5)
+    ent_disks.insert(0, str(gbl_num_disks))
+    ent_disks.bind('<Return>', get_ent)
+    ent_disks.bind('<FocusOut>', get_ent)
+    ent_disks.pack(side=tk.LEFT, padx=5)
+    btn_start = tk.Button(tk_row, text="Start", width=6)
+    btn_start.bind('<ButtonRelease-1>', run_hanoi)
+    btn_start.pack(side=tk.LEFT, padx=5)
+    btn_reset = tk.Button(tk_row, text="Reset", width=6)
+    btn_reset.bind('<ButtonRelease-1>', reset_hanoi)
+    btn_reset.pack(side=tk.LEFT, padx=5)
+    tk.Label(tk_row, text="Speed: ").pack(side=tk.LEFT)
+    tk_var = tk.StringVar(gbl_tkroot)
+    tk_var.set('normal')
+    tk_opt_menu = tk.OptionMenu(tk_row, tk_var,
+                  *{'slow', 'normal', 'fastest'})
+    tk_opt_menu.config(width = 6)
+    tk_opt_menu.pack(side=tk.LEFT)
+    tk_row.pack(side=tk.TOP, pady=5)
+
+    # animation canvas
+    gbl_canvas = tk.Canvas(gbl_tkroot, width=CANVAS_W, height=CANVAS_H)
+    gbl_canvas.pack()
+
+    def change_speed(*args):
+        global gbl_speed
+        speed_opt = {'slow': 0.002, 'normal': 0.001, 'fastest': 0}
+        gbl_speed = speed_opt.get(tk_var.get())
+        # print(gbl_speed)
+
+    tk_var.trace('w', change_speed)
+
+
+def run_hanoi(event):
+    global gbl_ready
+
+    if gbl_ready:
+        gbl_ready = False
+        try:
+            hanoi(gbl_num_disks-1, 0, 1, 2)
+        except Exception as err:
+            print(f'forced reset: {repr(err)}')
+    else:
+        pass
+
+
+def reset_hanoi(event):
+    draw_init_setting()
+
+
+def draw_init_setting():
+    global gbl_pegs, gbl_disks, gbl_pegstate, gbl_ready
+    gbl_pegs = []
+    gbl_pegstate = [[], [], []]
+    gbl_disks = []
+
+    gbl_canvas.delete('all')
+    # draw the three pegs a, b, c
+    peg_w = 10
+    peg_h = CANVAS_H // 2
+    peg_dist = CANVAS_W // 3
+    x1, y1 = (peg_dist - peg_w) // 2, CANVAS_H // 3
+    x2, y2 = x1 + peg_w, y1 + peg_h
+
+    for i in range(3):
+        gbl_pegs.append(gbl_canvas.create_rectangle(x1, y1, x2, y2, fill = 'black'))
+        x1 += peg_dist
+        x2 += peg_dist
+    gbl_tkroot.update_idletasks()
+    gbl_tkroot.update()
+
+    # create disks on the first peg
+    disk_h = peg_h // 16
+    disk_maxw = peg_dist * 2 // 3
+    disk_minw = 2 * peg_w
+    x1, y1 = (peg_dist - disk_maxw) // 2, y2 - disk_h - GAP
+    x2, y2 = x1 + disk_maxw, y1 + disk_h
+    dx = (disk_maxw - disk_minw) // (2 * max(1, gbl_num_disks-1))
+    dx = min(dx, 2 * peg_w)
+
+    for i in range(gbl_num_disks):
+        gbl_disks.insert(0, gbl_canvas.create_rectangle(x1, y1, x2, y2, fill = 'red'))
+        gbl_pegstate[0].append(gbl_num_disks - i - 1)
+        x1 += dx
+        x2 -= dx
+        y1 -= disk_h + GAP
+        y2 -= disk_h + GAP
+        gbl_tkroot.update_idletasks()
+        gbl_tkroot.update()
+
+    gbl_ready = True
+
+def move_disk(i, a, b):
+    global gbl_pegstate, gbl_canvas
+    disk_num = gbl_pegstate[a].pop()
+    if disk_num != i:
+        raise RuntimeError(f'Trying to move disk piece #{i} from peg {a}\
+                            to peg {b} that does not exist.')
+    disk = gbl_disks[i]
+
+    # Lift the disk above peg a
+    px1, py1, px2, py2 = gbl_canvas.bbox(gbl_pegs[a])
+    while True:
+        x1, y1, x2, y2 = gbl_canvas.bbox(disk)
+        if y2 < py1:
+            break
+        gbl_canvas.move(disk, 0, -1)
+        gbl_tkroot.update_idletasks()
+        gbl_tkroot.update()
+        time.sleep(gbl_speed)
+
+    # Move to peg b
+    px1, py1, px2, py2 = gbl_canvas.bbox(gbl_pegs[b])
+    new_center = (px1 + px2) // 2
+    while True:
+        x1, y1, x2, y2 = gbl_canvas.bbox(disk)
+        center = (x1 + x2) // 2
+        if center == new_center:
+            break
+        if center > new_center:
+            gbl_canvas.move(disk, -1, 0)
+        else:
+            gbl_canvas.move(disk, 1, 0)
+        gbl_tkroot.update_idletasks()
+        gbl_tkroot.update()
+        time.sleep(0.7*gbl_speed) # faster
+
+    # Drop down
+    disk_h = y2 - y1
+    new_bottom = py2 - disk_h * len(gbl_pegstate[b]) - GAP
+    while True:
+        x1, y1, x2, y2 = gbl_canvas.bbox(disk)
+        if y2 >= new_bottom:
+            break
+        gbl_canvas.move(disk, 0, 1)
+        gbl_tkroot.update_idletasks()
+        gbl_tkroot.update()
+        time.sleep(gbl_speed)
+
+    gbl_pegstate[b].append(i)
+
+
+def hanoi(n, a, b, c):
+    '''
+    Hanoi algorithm: move n pieces from a to c, using b as buffer.
+    For each move, call animate() to show the move
+    '''
+
+    if n < 0:
+        return
+    hanoi(n-1, a, c, b)
+    move_disk(n, a, c) # move nth piece from peg a to peg c
+    hanoi(n-1, b, a, c)
+
+
+def main():
+
+    setup_gui()
+    draw_init_setting()
+
+    # input("Press Enter to continue")
+
+    # try:
+    #     hanoi(gbl_num_disks-1, 0, 1, 2)
+    # except Exception as err:
+    #     print("aborted: " + repr(err))
+
+    gbl_tkroot.mainloop()
+
+
+if __name__ == "__main__":
+    main()