import tkinter as tki

class MyApp:
    def __init__(self,parent):
        self._parent = parent

        # add a canvas to draw on
        self._canvas = tki.Canvas(parent, width=200, height=200,
                                  highlightbackground='black')
        self._canvas.pack()

        # bind an event to the entry into the canvas
        self._canvas.bind("<Enter>", self._enter_event_handler)
        self._canvas.bind("<Leave>",
            lambda event: self._canvas.config(highlightbackground="black"))

    def _enter_event_handler(self,event):
        self._canvas.config(highlightbackground="red")

root = tki.Tk()
MyApp(root)
root.mainloop()