来自graphics.py的线对象没有绘图

Question

I'm using python graphics module (John Zelle). I have never had a problem before, I might just be overlooking something but I can't find it. I'm trying to draw a tic tac toe board. The lines are not drawing in. The Shell says the error is in graphics.py but I have redownloaded it from different sources, skimmed it over even, and cannot figure out what I'm doing wrong. Please help.

---

#here is my code sample
#import graphics library
from graphics import *
#build interface
def interface():
    win = GraphWin("Tic Tac Toe", 600,700)
    win.setCoords(8,1,6,1)
    #horizontal line #1
    h1 = Line(Point(2,1),Point(2,5))
    h1.draw(win)
#...there is more but it's repetitive so I won't waste time.

>>> interface()
Traceback (most recent call last):
  File ".../test.py", line 12, in <module>
    interface()
  File ".../test.py", line 10, in interface
    h1.draw(win)
  File "/LIB/graphics.py", line 450, in draw
    self.id = self._draw(graphwin, self.config)
  File "/LIB/graphics.py", line 627, in _draw
    x1,y1 = canvas.toScreen(p1.x,p1.y)
  File "/LIB/graphics.py", line 335, in toScreen
    return self.trans.screen(x,y)
  File "/LIB/graphics.py", line 386, in screen
    ys = (self.ybase-y) / self.yscale
ZeroDivisionError: float division by zero

Answer 1

After a bit of digging through the inner mechanics of graphics.py I noticed you have something a bit perculiar:

win.setCoords(8,1,6,1)

This seems a bit odd to me looking at the docstring:

Set coordinates of window to run from (x1,y1) in the lower-left corner to (x2,y2) in the upper-right corner.

Note that if you are using IDLE you can see this doc string by making win global or doing GraphWin.setCoords( and the docstring should appear on the (

So you are defining your screen to span from (8,1) in the bottom left corner to (6,1) in the top right corner... wait, what?

This means that not only your x coordinates are very backwards, but the line Line(Point(2,1),Point(2,5)) is not even in the x span of 8-6 .

And height of your canvas spans from 1 to 1, as in it has a height of 0 resulting in undefined behaviour. (hence the ZeroDivisionError )

I think you want a span more like:

win.setCoords(0,0,6,7)

This will get stuff properly displaying on your screen, although I expect you to adjust the exact numbers appropriately :)