You can simply do that with print(polygon.getPoints())
in your main method, which gives you [Point(60.0, 80.0), Point(50.0, 70.0), Point(70.0, 20.0), Point(90.0, 50.0), Point(100.0, 80.0)]
as output.
Example code:
import math
import graphics #must be included
from graphics import* # must be included
def main():
win = graphics.GraphWin("Exercise 2, Polygon", 500, 500)
#denotes window size
win.setBackground("black")
polygon = Polygon(Point(60,80),Point(50,70),Point(70,20),Point(90,50),Point(100,80))
#Include "Point" in the statement, else it wouldn't work
polygon.setOutline("yellow")
polygon.setWidth(5)
polygon.draw(win)
print(polygon.getPoints())
main()