I cannot reproduce any problems with this example. In my tests it gives a rectangular contour with a rectangular hole in the center. Please send me a complete script with some example output and information on your platform and versions of python and Polygon.

Jörg

Thanks for the effort! However, I have a question and I am not sure if it is GPC related or in any case if there is something that can be done about it.

My problem is when I want to add multiple polygons that leave a hole in the center. For example,

import Polygon.Shapes as ps
from math import pi

polys = [ps.Polygon([[1,1], [4,1],[4,2],[1,2]], hole = True) for i in range(4)]
polys[1].rotate(pi/2,1,1)
polys[1].shift(1,0)
polys[2].shift(0,2)
polys[3].rotate(pi/2,1,1)
polys[3].shift(3,0)
pp = reduce(lambda x,y: x+y, polys)

In principle these 4 rectangles should leave an empty square in the center. However, the result is a square with filled in center.

I want to have polygons with multiple holes when I make an union.

Thanks!
Best regards,
Jorge

Also thanks for the fantastic library, it has been very useful, especially since there aren’t many libraries like it in Python.

I changed a check function in the C library. Now instances of subclasses should be accepted by most methods. The changes are checked into the git repository at

https://bitbucket.org/jraedler/polygon2 ,
https://bitbucket.org/jraedler/polygon3 .

There are no packages, you have to download or checkout the master branch and compile it yourself.

Greetings,
Jörg

I don’t _need_ to subclass Polygon, but it is nice to add the methods I need to it.

I’m a little new to working with C libraries and I have a problem subclassing Polygon. Maybe you could help?

I have my code:
import Polygon as poly
class Shape(poly.Polygon):
def __init__(self, points):
super().__init__(points)
def __contains__(self, shape):
return shape.overlaps(self)

a = Shape(list of points)
b = Shape(some more points)

a in b
Here I will run into trouble for using the wrong type of arguments.

I changed the code to look like:
_shape = poly.Polygon(shape[0])
_self = poly.Polygon(self[0])
return _shape.overlaps(_self)

But it seems like a rather awkward solution. Any ideas?

Good luck, Joerg

Traceback (most recent call last):
File “”, line 1, in
File “Polygon/__init__.py”, line 5, in
from Polygon.cPolygon import *
ImportError: No module named cPolygon

Hope you can help me please. I’d be really grateful to you.
Cheers.
Wronzio

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