Someone know if it's possible to change the color of a pixel in a canvas without using un object, so without using something like canvas.create_oval or canvas.create_rectangle ?
Within tkinter itself, it's impossible.
Even if you manage to change a pixel on canvas window (which is possible with X11 and Windows APIs in a platform-dependent way), you'd have to ensure it's repainted properly.
You can, of course, place a frame of size 1x1 over the canvas, with a background color you want. This way, pixel is "changed" and no canvas object is created. If there's a real (though strange) problem behind a question, this trick could be a solution.
Change the color of a pixel in a canvas, Tkinter, Python