from Tkinter import *

def move():
    global listcoordx,listcoordy,bal,listdx,listdy
    dx=int(listdx[bal])
    listcoordx[bal]=int(listcoordx[bal])
    if listcoordx[bal]>380 or listcoordx[bal]<20 :
        dx=-dx
        listdx[bal]=dx
    listcoordx[bal]=listcoordx[bal]+dx
    dy=int(listdy[bal])
    listcoordy[bal]=int(listcoordy[bal])
    if listcoordy[bal]>380 or listcoordy[bal]<20 :
        dy=-dy
        listdy[bal]=dy
    listcoordy[bal]=listcoordy[bal]+dy
    can.coords(listbal[bal],listcoordx[bal]-20,listcoordy[bal]-20,listcoordx[bal]+20,listcoordy[bal]+20)
    bal=bal+1
    if bal==4:
        bal=0
    if flag==1:
        fen.after(1,move)    
         
def go():
    global flag,b
    if flag==0:
        flag=1
        move()
        
def stop():
    global flag
    flag=0
def quit():
    fen.destroy()  

fen=Tk()
listbal=['b1','b2','b3','b4']
listcoordx=['50','300','50','300']
listcoordy=['50','50','300','300']
listdx=['5','5','5','5']
listdy=['5','5','5','5']
listcoul=['red','blue','green','yellow']
flag,bal=0,0
can=Canvas(fen,width=400,height=400,bg='dark grey')
can.grid(row=1,column=1,rowspan=3)

while bal<len(listbal):
    x=int(listcoordx[bal])
    y=int(listcoordy[bal])
    listbal[bal]=can.create_oval(x-20,y-20,x+20,y+20,fill=listcoul[bal])
    bal=bal+1
bal=0

bout1=Button(text='Go!',command=go)
bout1.grid(row=1,column=2)
bout2=Button(text='Stop!',command=stop)
bout2.grid(row=2,column=2)
bout3=Button(text='Quitter',command=quit)
bout3.grid(row=3,column=2)

fen.mainloop()