# Tk_bind_by_key.py

# Tk_bind_by_key.py

try:
    import tkinter as tk  # using Python 3
except ImportError:
    import Tkinter as tk  # using Python 2

class Cv(): pass
cv=Cv()

def mvU(event):
    cv.y1 -= 10
    cv.y2 -= 10
    mv()

def mvD(event):
    cv.y1 += 10
    cv.y2 += 10
    mv()

def mvL(event):
    cv.x1 -= 10
    cv.x2 -= 10
    mv()

def mvR(event):
    cv.x1 += 10
    cv.x2 += 10
    mv()

def mv():
    oval = (cv.x1, cv.y1, cv.x2, cv.y2)
    canvas.coords(oval_id, oval)

m = tk.Tk()

canvas = tk.Canvas(m)
canvas.pack(expand=1, fill='both')
cv.x1, cv.x2 = 200, 250
cv.y1, cv.y2 = 100, 150
oval = (cv.x1, cv.y1, cv.x2, cv.y2)
oval_id = canvas.create_oval(oval)
canvas.bind_all('<w>', mvU)
canvas.bind_all('<s>', mvD)
canvas.bind_all('<a>', mvL)
canvas.bind_all('<d>', mvR)

m.mainloop()