conway's game of life / Single Responsibility Principle

[Mekire]

You need to pass it the canvas object.  Something like

def main():
    window = tk.Tk()
    window.title("conway's game of life")
    canvas = tk.Canvas(window, width=1200, height=900, bd=0, highlightthickness=0)
    canvas.pack()    

    bind_keys(canvas)

    cells = setup_phase(window, canvas)
    main_phase(cells, window, canvas)