A basic implementation of the __geo_interface__
Project description
Introduction
PyGeoIf provides a GeoJSON-like protocol for geo-spatial (GIS) vector data.
see https://gist.github.com/2217756
Other Python programs and packages that you may have heard of already implement this protocol:
So when you want to write your own geospatial library with support for this protocol you may use pygeoif as a starting point and build your functionality on top of it
You may think of pygeoif as a ‘shapely ultralight’ which lets you construct geometries and perform very basic operations like reading and writing geometries from/to WKT, constructing line strings out of points, polygons from linear rings, multi polygons from polygons, etc. It was inspired by shapely and implements the geometries in a way that when you are familiar with shapely you feel right at home with pygeoif
It was written to provide clean and python only geometries for fastkml
PyGeoIf is continually tested with Travis CI
Example
>>> from pygeoif import geometry
>>> p = geometry.Point(1,1)
>>> p.__geo_interface__
{'type': 'Point', 'coordinates': (1.0, 1.0)}
>>> print p
POINT (1.0 1.0)
>>> p1 = geometry.Point(0,0)
>>> l = geometry.LineString([p,p1])
>>> l.bounds
(0.0, 0.0, 1.0, 1.0)
>>> dir(l)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__',
'__geo_interface__', '__getattribute__', '__hash__', '__init__',
'__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
'__setattr__', '__sizeof__', '__str__', '__subclasshook__',
'__weakref__', '_coordinates', '_geoms', '_type', 'bounds', 'coords',
'geom_type', 'geoms', 'to_wkt']
>>> print l
LINESTRING (1.0 1.0, 0.0 0.0)
You find more examples in the test_main.py file which cover every aspect of pygeoif or in fastkml.
Classes
All classes implement the attribute:
__geo_interface__: as dicussed above
All geometry classes implement the attributes:
geom_type: Returns a string specifying the Geometry Type of the object
bounds: Returns a (minx, miny, maxx, maxy) tuple (float values) that bounds the object.
wkt: Returns the ‘Well Known Text’ representation of the object
and the method:
to_wkt which also prints the object
GeoObject
Base class for Geometry, Feature, and FeatureCollection
Geometry
Base class for geometry objects. Inherits from Geoobject.
Point
A zero dimensional geometry
A point has zero length and zero area.
Attributes
- x, y, zfloat
Coordinate values
Example
>>> p = Point(1.0, -1.0) >>> print p POINT (1.0000000000000000 -1.0000000000000000) >>> p.y -1.0 >>> p.x 1.0
LineString
A one-dimensional figure comprising one or more line segments
A LineString has non-zero length and zero area. It may approximate a curve and need not be straight. Unlike a LinearRing, a LineString is not closed.
Attributes
- geomssequence
A sequence of Points
LinearRing
A closed one-dimensional geometry comprising one or more line segments
A LinearRing that crosses itself or touches itself at a single point is invalid and operations on it may fail.
A Linear Ring is self closing
Polygon
A two-dimensional figure bounded by a linear ring
A polygon has a non-zero area. It may have one or more negative-space “holes” which are also bounded by linear rings. If any rings cross each other, the geometry is invalid and operations on it may fail.
Attributes
- exteriorLinearRing
The ring which bounds the positive space of the polygon.
- interiorssequence
A sequence of rings which bound all existing holes.
MultiPoint
A collection of one or more points
Attributes
- geomssequence
A sequence of Points
MultiLineString
A collection of one or more line strings
A MultiLineString has non-zero length and zero area.
Attributes
- geomssequence
A sequence of LineStrings
MultiPolygon
A collection of one or more polygons
Attributes
- geomssequence
A sequence of Polygon instances
GeometryCollection
A heterogenous collection of geometries (Points, LineStrings, LinearRings and Polygons)
Attributes
- geomssequence
A sequence of geometry instances
Please note: GEOMETRYCOLLECTION isn’t supported by the Shapefile format. And this sub-class isn’t generally supported by ordinary GIS sw (viewers and so on). So it’s very rarely used in the real GIS professional world.
Example
>>> from pygeoif import geometry
>>> p = geometry.Point(1.0, -1.0)
>>> p2 = geometry.Point(1.0, -1.0)
>>> geoms = [p, p2]
>>> c = geometry.GeometryCollection(geoms)
>>> c.__geo_interface__
{'type': 'GeometryCollection', 'geometries': [{'type': 'Point', 'coordinates': (1.0, -1.0)},/
{'type': 'Point', 'coordinates': (1.0, -1.0)}]}
>>> [geom for geom in geoms]
[Point(1.0, -1.0), Point(1.0, -1.0)]
Feature
Aggregates a geometry instance with associated user-defined properties.
Attributes
- geometryobject
A geometry instance
- propertiesdict
A dictionary linking field keys with values associated with with geometry instance
Example
>>> p = Point(1.0, -1.0)
>>> props = {'Name': 'Sample Point', 'Other': 'Other Data'}
>>> a = Feature(p, props)
>>> a.properties
{'Name': 'Sample Point', 'Other': 'Other Data'}
>>> a.properties['Name']
'Sample Point'
FeatureCollection
A heterogenous collection of Features
Attributes
- features: sequence
A sequence of feature instances
Example
>>> from pygeoif import geometry
>>> p = geometry.Point(1.0, -1.0)
>>> props = {'Name': 'Sample Point', 'Other': 'Other Data'}
>>> a = geometry.Feature(p, props)
>>> p2 = geometry.Point(1.0, -1.0)
>>> props2 = {'Name': 'Sample Point2', 'Other': 'Other Data2'}
>>> b = geometry.Feature(p2, props2)
>>> features = [a, b]
>>> c = geometry.FeatureCollection(features)
>>> c.__geo_interface__
{'type': 'FeatureCollection', 'features': [{'geometry': {'type': 'Point', 'coordinates': (1.0, -1.0)},/
'type': 'Feature', 'properties': {'Other': 'Other Data', 'Name': 'Sample Point'}},/
{'geometry': {'type': 'Point', 'coordinates': (1.0, -1.0)}, 'type': 'Feature',/
'properties': {'Other': 'Other Data2', 'Name': 'Sample Point2'}}]}
>>> [feature for feature in c]
[<Feature Instance Point geometry 2 properties>, <Feature Instance Point geometry 2 properties>]
Functions
as_shape
Create a pygeoif feature from an object that provides the __geo_interface__
>>> from shapely.geometry import Point >>> from pygeoif import geometry >>> geometry.as_shape(Point(0,0)) <pygeoif.geometry.Point object at 0x...>
from_wkt
Create a geometry from its WKT representation
>>> p = geometry.from_wkt('POINT (0 1)')
>>> print p
POINT (0.0 1.0)
signed_area
Return the signed area enclosed by a ring using the linear time algorithm at http://www.cgafaq.info/wiki/Polygon_Area. A value >= 0 indicates a counter-clockwise oriented ring.
orient
Returns a copy of the polygon with exterior in counter-clockwise and interiors in clockwise orientation for sign=1.0 and the other way round for sign=-1.0
mapping
Returns the __geo_interface__ dictionary
Development
Installation
You can install PyGeoIf from pypi using pip:
pip install pygeoif
Testing
In order to provide a Travis-CI like testing of the PyGeoIf package during development, you can use tox (pip install tox) to evaluate the tests on all supported Python interpreters which you have installed on your system.
You can run the tests with tox --skip-missin-interpreters and are looking for output similar to the following:
______________________________________________________ summary ______________________________________________________ SKIPPED: py26: InterpreterNotFound: python2.6 py27: commands succeeded SKIPPED: py32: InterpreterNotFound: python3.2 SKIPPED: py33: InterpreterNotFound: python3.3 py34: commands succeeded SKIPPED: pypy: InterpreterNotFound: pypy SKIPPED: pypy3: InterpreterNotFound: pypy3 congratulations :)
You are primarily looking for the congratulations :) line at the bottom, signifying that the code is working as expected on all configurations available.
Changelog
0.7 (2017/05/04)
fix broken multipolygon [mindflayer]
add “bbox” to __geo_interface__ output [jzmiller1]
0.6 (2015/08/04)
Add id to feature [jzmiller1]
0.5 (2015/07/13)
Add __iter__ method to FeatureCollection and GeometryCollection [jzmiller1].
add pypy and pypy3 and python 3.4 to travis.
Add tox configuration for performing local testing [Ian Lee].
Add Travis continuous deployment.
0.4 (2013/10/25)
after a year in production promote it to Development Status :: 5 - Production/Stable
MultiPolygons return tuples as the __geo_interface__
0.3.1 (2012/11/15)
specify minor python versions tested with Travis CI
fix for signed area
0.3 (2012/11/14)
add GeometryCollection
len(Multi*) and len(GeometryCollection) returns the number of contained Geometries
add orient function to get clockwise or counterclockwise oriented poygons
add signed_area function
add _set_orientation method to lineStrings, Polygons and MultiPolygons
0.2.1 (2012/08/02)
as_shape also accepts an object that is neither a dictionary nor has a __geo_interface__ but can be converted into a __geo_interface__ compliant dictionary
0.2 (2012/08/01)
change license to LGPL
add wkt as a property
as_shape also accepts a __geo_interface__ compliant dictionary
test with python3
0.1 (2012/07/27)
initial release
Release history Release notifications | RSS feed
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