pygeos 0.1

GEOS wrapped in numpy ufuncs

This is a C/Python library that wraps geometry functions in GEOS in numpy ufuncs. This project is still in a mock-up phase: the API will most likely change.

The Geometry Array dtype

Shapely geometries are stored in structured numpy arrays with the following structure:

np.dtype([("obj", "O"), ("_ptr", "intp")])

In this way, we enable fast C-access to the geometries, while keeping a python object close to keep track of the memory allocation/deallocation.

The ufuncs automatically converts a (iterable of) shapely geometry to this Geometry Array dtype. Functions that return geometries will return this custom dtype.

Examples

Compare an grid of points with a polygon:

>>> from pygeos import contains
>>> from shapely.geometry import box, Point

>>> points = [[Point(i, j) for i in range(4)] for j in range(4)]
>>> polygon = box(0, 0, 2, 2)

>>> contains(polygon, points)

  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 area, intersection
>>> from shapely.geometry import box

>>> polygons_x = [[box(0 + i, 0, 10 + i, 10) for i in range(5)]]
>>> polygons_y = [[box(0, 0 + j, 10, 10 + j)] for j in range(5)]

>>> area(intersection(polygons_x, polygons_y))

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.