# Tk_drag_and_drop.py

# Tk_drag_and_drop.py
from Tkinter import *

def Click(event):
    X = event.x
    Y = event.y

    [xmin,ymin,xmax,ymax] = canvas.coords(target)
    cv.onTarget = False
    if xmin<X<xmax and ymin<Y<ymax: cv.onTarget = True

def Drag(event):
    X = event.x
    Y = event.y

    if cv.onTarget == True:
        if X<0: X=0
        if X>L: X=L
        if Y<0: Y=0
        if Y>H: Y=H
        canvas.coords(target,X-sq,Y-sq,X+sq,Y+sq)

root = Tk()
root.title("Drag and Drop")

L = 480
H = 160
sq = 20
canvas = Canvas(root,width=L,height=H,bg ='white')
target = canvas.create_rectangle(0,0,sq*2,sq*2,fill='maroon')

class Cv():
    onTarget = False
cv = Cv()
canvas.bind('<Button-1>',Click)
canvas.bind('<B1-Motion>',Drag)

canvas.focus_set()
canvas.pack(padx=10,pady=10)

root.mainloop()