Comments on: Point in Polygon in Python

By: Neil

Neil — Tue, 25 Aug 2009 15:36:55 +0000

For other google searchers, there is a fast version of this code in the python plotting library, matplotlib:

>>> from matplotlib.nxutils import points_inside_poly
>>> help(points_inside_poly)
points_inside_poly(…)
mask = points_inside_poly(xypoints, xyverts)

Return a boolean ndarray, True for points inside the polygon.

*xypoints*
a sequence of N x,y pairs.
*xyverts*
sequence of x,y vertices of the polygon.
*mask* an ndarray of length N.

A point on the boundary may be treated as inside or outside.
See `pnpoly `_

By: Justin Bronn

Justin Bronn — Sun, 01 Feb 2009 19:34:38 +0000

You could’ve just stopped at GeoDjango . It includes the original ctypes interface to GEOS, and has Point and Polygon objects that expose all of the geometric operations that GEOS provides. Good suggestion about having “point in polygon” phrase in the docs, and I’ll try to incorporate it into GeoDjango’s GEOS docs: http://geodjango.org/docs/geos.html. Here’s an example:

>>> from django.contrib.gis.geos import Point, Polygon
>>> pnt = Point(1, 1)
>>> poly = Polygon( ((0, 0), (0, 2), (2, 2), (2, 0), (0, 0)) )
>>> poly.contains(pnt)
True
>>> pnt.within(poly)
True

By: Dan

Dan — Wed, 28 Jan 2009 16:35:47 +0000

I was looking for the exact same thing two days ago. I found this snippet on the Python list from somebody calling themselves Guido

http://mail.python.org/pipermail/python-list/1999-September/012609.html

Do a search for Paul Burke’s original page (the link in the mail is dead), as it explains the algorithms a lot more clearly.

By: Paddy3118

Paddy3118 — Tue, 27 Jan 2009 20:03:06 +0000

Snap! What's in a name? - Paddy.