Geospatial geometries, predicates, and operations
Project description
Shapely is a Python package for programming with 2D geospatial geometries. It is based on GEOS (http://geos.refractions.net). Shapely 1.0 is ignorant about coordinate and reference systems. Projection responsibility is left to specific applications. For more information, see:
Shapely requires Python 2.4+. (I’ve also begun to port it to Python 3.0: http://zcologia.com/news/564/shapely-for-python-3-0/.)
Dependencies
libgeos_c (2.2.3 or 3.0.0+)
Python ctypes (standard in Python 2.5+)
Installation
Windows users should use the executable installer, which contains the required GEOS DLL. Other users should acquire libgeos_c by any means, make sure that it is on the system library path, and install from the Python package index:
$ sudo easy_install Shapely
with the setup script:
$ sudo python setup.py install
or by using the development buildout on Linux, which also provides libgeos_c:
$ svn co http://svn.gispython.org/svn/gispy/buildout/shapely.buildout/trunk shapely.buildout $ cd shapely.buildout $ python bootstrap.py $ ./bin/buildout
Usage
To buffer a point:
>>> from shapely.geometry import Point >>> point = Point(-106.0, 40.0) # longitude, latitude >>> point.buffer(10.0) <shapely.geometry.polygon.Polygon object at ...>
See the manual for comprehensive examples of usage. See also Operations.txt and Predicates.txt under tests/ for more examples of the spatial operations and predicates provided by Shapely. See also Point.txt, LineString.txt, etc for examples of the geometry APIs.
Numpy integration
All Shapely geometry instances provide the Numpy array interface:
>>> from numpy import asarray >>> a = asarray(point) >>> a.size 3 >>> a.shape (2,)
Numpy arrays can also be adapted to Shapely points and linestrings:
>>> from shapely.geometry import asLineString >>> a = array([[1.0, 2.0], [3.0, 4.0]]) >>> line = asLineString(a) >>> line.wkt 'LINESTRING (1.0000000000000000 2.0000000000000000, 3.0000000000000000 4.0000000000000000)'
Python Geo Interface
Any object that provides the Python geo interface can be adapted to a Shapely geometry with the asShape factory:
>>> d = {"type": "Point", "coordinates": (0.0, 0.0)}
>>> from shapely.geometry import asShape
>>> shape = asShape(d)
>>> shape.geom_type
'Point'
>>> tuple(shape.coords)
((0.0, 0.0),)
>>> class GeoThing(object):
... def __init__(self, d):
... self.__geo_interface__ = d
>>> thing = GeoThing({"type": "Point", "coordinates": (0.0, 0.0)})
>>> shape = asShape(thing)
>>> shape.geom_type
'Point'
>>> tuple(shape.coords)
((0.0, 0.0),)
See http://trac.gispython.org/projects/PCL/wiki/PythonGeoInterface for more details on the interface.
Testing
Several of the modules have docstring doctests:
$ cd shapely $ python point.py
There are also two test runners under tests/. test_doctests.py requires zope.testing. runalldoctests.py does not. Perhaps the easiest way to run the tests is:
$ python setup.py test
Support
For current information about this project, see the wiki.
If you have questions, please consider joining our community list:
Credits
Sean Gillies (Pleiades)
Howard Butler (Hobu, Inc.)
Kai Lautaportti (Hexagon IT)
Frédéric Junod (Camptocamp SA)
Eric Lemoine (Camptocamp SA)
Justin Bronn (GeoDjango) for ctypes inspiration
Artem Pavlenko (Mapnik) for help with GEOS DLLs
Major portions of this work were supported by a grant (to Pleiades) from the U.S. National Endowment for the Humanities (http://www.neh.gov).
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