python - Cartesian coordinate system for tkinter? -

i interested in animating geometric algorithms learned in python using gui toolkit such tkinter or wxpython.

while reading tkinter tutorials 1 of odd things (well @ least graphics newbie me) coordinate system used positioning objects not standard cartesian coordinate system, origin be, say, @ center of screen, , x-coordinates increase right , y-coordinates increase upwards.

for tkinter origin @ top left corner , x-coordinates increase right , y-coordinates decrease downward. can make tkinter use cartesian system in previous paragraph?

the final goal make interactive program, create window, cartesian x,y axes , user inputs points using mouse-clicks , construction of geometric object such convex hull of points animated on same canvas.