pygeos 0.2

The Geometry object

GEOS geometry objects are stored in a Python extension type pygeos.GEOSGeometry, that keeps the python interpreter out of the numpy ufunc inner loop. This object calls the GEOS destroy function to deallocate memory just before the wrapping GEOSGeometry object is deallocated.

Ufuncs only act on these pygeos.GEOSGeometry objects. Construct these as follows. This operation copies the underlying C object so that we can safely deallocate it once point is garbage collected:

>>> from pygeos import GEOSGeometry
>>> from shapely.geometry import Point

>>> pointer_to_geometry = Point(i, j)._geom
>>> geometry = GEOSGeometry(pointer_to_geometry)

Or simply:

>>> from pygeos import points

>>> point = points(5.2, 52.1)

Examples

Compare an grid of points with a polygon:

>>> geoms = points(*np.indices((4, 4)))
>>> polygon = box(0, 0, 2, 2)

>>> contains(polygon, geoms)

  array([[False, False, False, False],
         [False,  True, False, False],
         [False, False, False, False],
         [False, False, False, False]])

Compute the area of all possible intersections of two lists of polygons:

>>> from pygeos import box, area, intersection

>>> polygons_x = box(range(5), 0, range(10, 15), 10)
>>> polygons_y = box(0, range(5), 10, range(10, 15))

>>> area(intersection(polygons_x[:, np.newaxis], polygons_y[np.newaxis, :]))

array([[100.,  90.,  80.,  70.,  60.],
     [ 90.,  81.,  72.,  63.,  54.],
     [ 80.,  72.,  64.,  56.,  48.],
     [ 70.,  63.,  56.,  49.,  42.],
     [ 60.,  54.,  48.,  42.,  36.]])

Installation

Pygeos uses shapely’s installing scripts. If you have libgeos at a standard location, the following should work:

$ pip install pygeos

Installation for developers

Clone the package:

$ git clone https://github.com/caspervdw/pygeos.git

Install it using pip:

$ pip install -e .

Run the unittests:

$ python -m pytest pygeos/test.py

References

• GEOS: http://trac.osgeo.org/geos

• Shapely: https://shapely.readthedocs.io/en/latest/

• Numpy ufuncs: https://docs.scipy.org/doc/numpy/reference/ufuncs.html

• Joris van den Bossche’s blogpost: https://jorisvandenbossche.github.io/blog/2017/09/19/geopandas-cython/

• Matthew Rocklin’s blogpost: http://matthewrocklin.com/blog/work/2017/09/21/accelerating-geopandas-1

Copyright & License

Copyright (c) 2019, Casper van der Wel. BSD 3-Clause license.