pygeoif 1.5.0

Description:

pygeoif 1.5.0

Introduction
PyGeoIf provides a GeoJSON-like protocol
for geo-spatial (GIS) vector data.
Other Python programs and packages that you may have heard of that
implement this protocol:

ArcPy
descartes
PySAL
Shapely
pyshp
GeoPandas
Karta
mapnik

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. It has no requirements outside the
Python standard library and is therefore easy to integrate into your
project. It is tested on CPython and
PyPy, but it should work on alternative
Python implementations (that implement the language specification >=3.8) as well.
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 pygeoif,
you will feel right at home with shapely or the other way round.
It provides Hypothesis strategies for all geometries for property based
testing with Hypothesis.
It was written to provide clean and python only geometries for fastkml


Installation
You can install PyGeoIf from pypi using pip:
pip install pygeoif



Example
>>> from pygeoif import geometry
>>> p = geometry.Point(1,1)
>>> p.__geo_interface__
{'type': 'Point', 'bbox': (1, 1, 1, 1), 'coordinates': (1, 1)}
>>> print(p)
POINT (1 1)
>>> p
Point(1, 1)
>>> l = geometry.LineString([(0.0, 0.0), (1.0, 1.0)])
>>> l.bounds
(0.0, 0.0, 1.0, 1.0)
>>> print(l)
LINESTRING (0.0 0.0, 1.0 1.0)
You find more examples in the
tests
directory which cover every aspect of pygeoif or in fastkml.


Classes
All classes implement the attribute:

__geo_interface__: as discussed above, an interface to GeoJSON.

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 that bounds the object.
wkt: Returns the ‘Well Known Text’ representation of the object

For two-dimensional geometries the following methods are implemented:

convex_hull: Returns a representation of the smallest convex Polygon containing
all the points in the object unless the number of points in the object is less than three.
For two points, the convex hull collapses to a LineString; for 1, a Point.
For three dimensional objects only their projection in the xy plane is taken into consideration.
Empty objects without coordinates return None for the convex_hull.


Point
A zero dimensional geometry
A point has zero length and zero area. A point cannot be empty.

Attributes

x, y, zfloat
Coordinate values




Example



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 LinearRing 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.

maybe_valid: boolean
When a polygon has obvious problems such as self crossing
lines or holes that are outside the exterior bounds this will
return False. Even if this returns True the geometry may still be invalid,
but if this returns False you do have a problem.





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 or GeoJSON 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)
>>> [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
>>> from pygeoif import Point, Feature
>>> 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 Point, Feature, FeatureCollection
>>> p = Point(1.0, -1.0)
>>> props = {'Name': 'Sample Point', 'Other': 'Other Data'}
>>> a = Feature(p, props)
>>> p2 = Point(1.0, -1.0)
>>> props2 = {'Name': 'Sample Point2', 'Other': 'Other Data2'}
>>> b = Feature(p2, props2)
>>> features = [a, b]
>>> c = FeatureCollection(features)
>>> [feature for feature in c]
[Feature(Point(1.0, -1.0), {'Name': 'Sample Point', 'Other': 'Other Data'},...]




Functions

shape
Create a pygeoif feature from an object that provides the __geo_interface__
or any GeoJSON compatible dictionary.
>>> from shapely.geometry import Point
>>> from pygeoif import geometry, shape
>>> shape(Point(0,0))
Point(0.0, 0.0)


from_wkt
Create a geometry from its WKT representation
>>> from pygeoif import from_wkt
>>> p = from_wkt('POINT (0 1)')
>>> print(p)
POINT (0.0 1.0)


signed_area
Return the signed area enclosed by a ring.
A value >= 0 indicates a counter-clockwise oriented ring.


orient
Returns a copy of a polygon with exteriors and interiors in the right orientation.
if ccw is True than the exterior will be in counterclockwise orientation
and the interiors will be in clockwise orientation, or
the other way round when ccw is False.


box
Return a rectangular polygon with configurable normal vector.


mapping
Return the __geo_interface__ dictionary.



Development
Clone this repository, create a virtualenv with Python 3.8 or later with
python3 -m venv .venv and activate it with source .venv/bin/activate.
Then install the requirements with pip install -e ".[dev]".

pre-commit
Install the pre-commit hook with:
pip install pre-commit
pre-commit install
and check the code with:
pre-commit run --all-files


Testing
Run the unit and static tests with:
pytest tests
pytest --doctest-glob="README.rst"
black pygeoif
ruff pygeoif
flake8 pygeoif
mypy pygeoif



Acknowledgments
The tests were improved with mutmut which discovered some nasty edge cases.