Why script run only 1 time?

Question

I wrote this code so that when I press on the image this image changes color. The problem is that click works only once; when I click a second time, nothing happens. Why?

immagine1 = Label(root, image=photo1)
immagine1.place(x=20, y=20)

def su1(event):
    print ("coordinate 1", event.x, event.y)
    clickX1 = event.x
    clickY1 = event.y
    if (clickX1 >= 10 and clickX1 <= 275 and clickY1 >= 10 and clickY1 <= 320):
        immagine1 = Label(root, image=photo2)
        immagine1.place(x=20, y=20)

def giu1(event):
    clickX1 = event.x
    clickY1 = event.y
    if (clickX1 >= 10 and clickX1 <= 275 and clickY1 >= 10 and clickY1 <= 320):
        immagine1 = Label(root, image=photo1)
        immagine1.place(x=20, y=20)

immagine1.bind("<Button-1>", su1)
immagine1.bind("<ButtonRelease-1>", giu1)

Correct:

immagine1 = Label(root, image=photo1)
immagine1.place(x=20, y=20)

def su1(event):
    print ("coordinate 1", event.x, event.y)
    clickX1 = event.x
    clickY1 = event.y
    if (clickX1 >= 10 and clickX1 <= 275 and clickY1 >= 10 and clickY1 <= 320):
        immagine1.configure(image=photo2)

def giu1(event):
    clickX1 = event.x
    clickY1 = event.y
    if (clickX1 >= 10 and clickX1 <= 275 and clickY1 >= 10 and clickY1 <= 320):
        immagine1.configure(image=photo1)

immagine1.bind("<Button-1>", su1)
immagine1.bind("<ButtonRelease-1>", giu1)

Answer 1

The problem seems to be this line:

immagine1 = Label(root, image=photo2)

Here you're re-assigning the immagine1 variable and therefore you're losing the bind that you did:

immagine1.bind("<Button-1>", su1)