Подскажите как в python вернуться на действие назад?

from Tkinter import *
import tkMessageBox
import Tkinter
import tkFileDialog
 
def donothing():
   print "a"
 
def file_save():
    name=asksaveasfile(mode='w',defaultextension=".txt")
    text2save=str(text.get(0.0,END))
    name.write(text2save)
    name.close
 
root = Tk()
root.geometry("500x500")
menubar=Menu(root)
text=Text(root)
text.pack()
filemenu=Menu(menubar,tearoff=0)
filemenu.add_command(label="New", command=donothing)
filemenu.add_command(label="Open", command=donothing)
filemenu.add_command(label="Save", command=file_save)
filemenu.add_command(label="Save as...", command=donothing)
filemenu.add_command(label="Close", command=donothing)
filemenu.add_separator()
filemenu.add_command(label="Exit", command=root.quit)
menubar.add_cascade(label="File", menu=filemenu)
 
editmenu=Menu(menubar,tearoff=0)
editmenu.add_command(label="Undo", command=donothing)
editmenu.add_command(label="Copy", command=donothing)
editmenu.add_command(label="Paste", command=donothing)
menubar.add_cascade(label="Edit", menu=editmenu)
 
helpmenu=Menu(menubar,tearoff=0)
helpmenu.add_command(label="Help",command=donothing)
menubar.add_cascade(label="Help",menu=helpmenu)
 
root.config(menu=menubar)
root.mainloop()

from tkinter import *
from tkinter.colorchooser import askcolor
from PIL import ImageGrab
 
 
class Paint(object):
 
    DEFAULT_PEN_SIZE = 5.0
    DEFAULT_COLOR = 'black'
 
    def __init__(self):
        self.root = Tk()
 
        self.pen_button = Button(self.root, text='pen', command=self.use_pen)
        self.pen_button.grid(row=0, column=0)
 
        self.brush_button = Button(self.root, text='brush', command=self.use_brush)
        self.brush_button.grid(row=0, column=1)
 
        self.color_button = Button(self.root, text='color', command=self.choose_color)
        self.color_button.grid(row=0, column=2)
 
        self.eraser_button = Button(self.root, text='eraser', command=self.use_eraser)
        self.eraser_button.grid(row=0, column=3)
 
        self.choose_size_button = Scale(self.root, from_=1, to=10, orient=HORIZONTAL)
        self.choose_size_button.grid(row=0, column=5)
 
        self.save_button = Button(self.root, text='save', command=self.saveImage)
        self.save_button.grid(row=0, column=4)
 
        self.c = Canvas(self.root, bg='white', width=600, height=600)
        self.c.grid(row=1, columnspan=5)
 
        self.setup()
        self.root.mainloop()
 
    def setup(self):
        self.old_x = None
        self.old_y = None
        self.line_width = self.choose_size_button.get()
        self.color = self.DEFAULT_COLOR
        self.eraser_on = False
        self.active_button = self.pen_button
        self.c.bind('<B1-Motion>', self.paint)
        self.c.bind('<ButtonRelease-1>', self.reset)
 
    def use_pen(self):
        self.activate_button(self.pen_button)
 
    def use_brush(self):
        self.activate_button(self.brush_button)
 
    def choose_color(self):
        self.eraser_on = False
        self.color = askcolor(color=self.color)[1]
 
    def use_eraser(self):
        self.activate_button(self.eraser_button, eraser_mode=True)
 
    def activate_button(self, some_button, eraser_mode=False):
        self.active_button.config(relief=RAISED)
        some_button.config(relief=SUNKEN)
        self.active_button = some_button
        self.eraser_on = eraser_mode
 
    def paint(self, event):
        self.line_width = self.choose_size_button.get()
        paint_color = 'white' if self.eraser_on else self.color
        if self.old_x and self.old_y:
            self.c.create_line(self.old_x, self.old_y, event.x, event.y,
                               width=self.line_width, fill=paint_color,
                               capstyle=ROUND, smooth=TRUE, splinesteps=36)
        self.old_x = event.x
        self.old_y = event.y
 
    def reset(self, event):
        self.old_x, self.old_y = None, None
 
    def saveImage(self):
        widget = self.c
        x = self.root.winfo_rootx() + widget.winfo_x()
        y = self.root.winfo_rooty()+ widget.winfo_y()
        x1 = x + widget.winfo_width()
        y1 = y + widget.winfo_height()
        ImageGrab.grab().crop((x, y, x1, y1)).save("paint.png")
 
 
if __name__ == '__main__':
    Paint()

from tkinter import *
import random
 
root = Tk()
 
colors = ['navy', 'slate blue', 'lime green',
          'purple', 'firebrick', 'salmon',
          'slate gray']
 
# Exit button
def exit():
    root.destroy()
 
b1 = Button(root, text="Exit", command=exit)
b1.pack(side=BOTTOM,padx=20)
 
 
def clear():
    canvas.delete('all')
 
clear_button = Button(root, text="Clear", command=clear)
clear_button.pack(side=BOTTOM, padx=20)
 
 
def undo():
    global MEMORY
    global CLICK_COUNTS
 
    number_to_delete = CLICK_COUNTS[-1]
    for index in range(-number_to_delete, 0):
        canvas.delete(MEMORY[index])
        del MEMORY[index]
 
    del CLICK_COUNTS[-1]
    
    
undo_button = Button(root, text="Undo", command=undo)
undo_button.pack(side=BOTTOM)
 
 
 
canvas = Canvas(root, width=400, height=400)
canvas.pack()
 
def get_pointer(event=None):
    x = root.winfo_pointerx() - root.winfo_rootx()
    y = root.winfo_pointery() - root.winfo_rooty()
    print("You clicked at {}, {}".format(x, y))
    return x, y
 
MEMORY = []
def draw_rectangle(x, y):
    shape = canvas.create_rectangle(
        x, y, x + 10, y + 10,
        fill=random.choice(colors))
    
    global MEMORY
    MEMORY.append(shape)
 
 
LOOP = True
CLICK_COUNTS = []
def draw(event=None):
    x, y = get_pointer()
    draw_rectangle(x, y)
    
    global CLICK_COUNTS
    CLICK_COUNTS[-1] = CLICK_COUNTS[-1] + 1
 
    global LOOP
    if LOOP:
        root.after(1, draw)
 
def start_draw(event=None):
    global CLICK_COUNTS
    CLICK_COUNTS.append(0)
    
    global LOOP
    LOOP = True
    draw()
 
 
 
def stop_draw(event=None):
    global LOOP
    LOOP = False
 
    global MEMORY
    print("There are {} shapes".format(len(MEMORY)))
 
 
canvas.bind('<Button-1>', start_draw)
canvas.bind('<ButtonRelease-1>', stop_draw)
 
root.mainloop()