from tkinter import *

def klahv(event):
   global x, y, r
   if event.keysym=="Left":  x=x-1
   if event.keysym=="Right": x=x+1
   if event.keysym=="Up":    y=y-1
   if event.keysym=="Down":  y=y+1
   ala.coords(ovaal, x, y, x+r, y+r)
   
aken = Tk()
ala = Canvas(aken, width=400, height=300, bg='white')
ala.pack()

x = 0
y = 10
r = 30

ovaal=ala.create_oval(x, y, x+r, y+r, fill="blue")
ala.bind("<Key>", klahv)
ala.focus_set()

aken.mainloop()