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:

* ArcPy http://help.arcgis.com/en/arcgisdesktop/

* descartes https://bitbucket.org/sgillies/descartes/

* geojson http://pypi.python.org/pypi/geojson/

* PySAL http://pysal.geodacenter.org/

* Shapely https://github.com/Toblerity/Shapely

So when you want to write your own geospatilal 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_

.. _fastkml: http://pypi.python.org/pypi/fastkml/

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

`tests.py <https://github.com/cleder/pygeoif/blob/master/pygeoif/tests.py>`_

file which cover every aspect of pygeoif or in fastkml_.

Classes

========

All classes implement the attributes:

* __geo_interface__: as dicussed above

* 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

Point

-----

A zero dimensional feature

Attributes

~~~~~~~~~~~

x, y, z : float

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

~~~~~~~~~~~

geoms : sequence

A sequence of Points

LinearRing

-----------

A closed one-dimensional feature 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 feature is invalid and operations on it may fail.

Attributes

~~~~~~~~~~~

exterior : LinearRing

The ring which bounds the positive space of the polygon.

interiors : sequence

A sequence of rings which bound all existing holes.

MultiPoint

----------

A collection of one or more points

Attributes

~~~~~~~~~~~

geoms : sequence

A sequence of Points

MultiLineString

----------------

A collection of one or more line strings

A MultiLineString has non-zero length and zero area.

Attributes

~~~~~~~~~~~

geoms : sequence

A sequence of LineStrings

MultiPolygon

-------------

A collection of one or more polygons

Attributes

~~~~~~~~~~~~~

geoms : sequence

A sequence of `Polygon` instances

GeometryCollection

-------------------

A heterogenous collection of geometries (Points, LineStrings, LinearRings

and Polygons)

Attributes

~~~~~~~~~~~

geoms : sequence

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.

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

Changelog

=========

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

============

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:

* ArcPy http://help.arcgis.com/en/arcgisdesktop/

* descartes https://bitbucket.org/sgillies/descartes/

* geojson http://pypi.python.org/pypi/geojson/

* PySAL http://pysal.geodacenter.org/

* Shapely https://github.com/Toblerity/Shapely

So when you want to write your own geospatilal 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_

.. _fastkml: http://pypi.python.org/pypi/fastkml/

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

`tests.py <https://github.com/cleder/pygeoif/blob/master/pygeoif/tests.py>`_

file which cover every aspect of pygeoif or in fastkml_.

Classes

========

All classes implement the attributes:

* __geo_interface__: as dicussed above

* 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

Point

-----

A zero dimensional feature

Attributes

~~~~~~~~~~~

x, y, z : float

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

~~~~~~~~~~~

geoms : sequence

A sequence of Points

LinearRing

-----------

A closed one-dimensional feature 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 feature is invalid and operations on it may fail.

Attributes

~~~~~~~~~~~

exterior : LinearRing

The ring which bounds the positive space of the polygon.

interiors : sequence

A sequence of rings which bound all existing holes.

MultiPoint

----------

A collection of one or more points

Attributes

~~~~~~~~~~~

geoms : sequence

A sequence of Points

MultiLineString

----------------

A collection of one or more line strings

A MultiLineString has non-zero length and zero area.

Attributes

~~~~~~~~~~~

geoms : sequence

A sequence of LineStrings

MultiPolygon

-------------

A collection of one or more polygons

Attributes

~~~~~~~~~~~~~

geoms : sequence

A sequence of `Polygon` instances

GeometryCollection

-------------------

A heterogenous collection of geometries (Points, LineStrings, LinearRings

and Polygons)

Attributes

~~~~~~~~~~~

geoms : sequence

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.

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

Changelog

=========

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

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