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A simple Python GeoJSON file reader and writer.

Project description

PyGeoj is a simple Python GeoJSON file reader and writer intended for end-users. It exposees dictionary structures as high level objects with convenience methods, so the user does not have to get caught up in the details of the format specification.

Platforms

Python 2 and 3.

Dependencies

Pure Python, no dependencies.

Installing it

PyGeoj is installed with pip from the commandline:

pip install pygeoj

It also works to just place the “pygeoj” package folder in an importable location like “PythonXX/Lib/site-packages”.

Example Usage

Begin by importing the pygeoj module:

import pygeoj

Reading

Reading geojson formatted GIS files is a simple one-liner (requires the geojson file to be a “FeatureCollection”):

testfile = pygeoj.load(filepath="testfile.geojson")
# or
testfile = pygeoj.load(data=dict(...))

Basic information about the geojson file can then be extracted, such as:

len(testfile) # the number of features
testfile.bbox # the bounding box region of the entire file
testfile.crs # the coordinate reference system
testfile.all_attributes # retrieves the combined set of all feature attributes
testfile.common_attributes # retrieves only those field attributes that are common to all features

Individual features can be accessed by their index in the features list:

testfile[3]
# or
testfile.get_feature(3)

Or by iterating through all of them:

for feature in testfile:
    # do something

A feature can be inspected in various ways:

feature.properties
feature.geometry.type
feature.geometry.coordinates
feature.geometry.bbox

Editing

The standard Python list operations can be used to edit and swap around the features in a geojson instance, and then saving to a new geojson file:

testfile[3] = testfile[8]
# or testfile.replace_feature(3, testfile[8])
del testfile[8]
# or testfile.remove_feature(8)
testfile.save("test_edit.geojson")

An existing feature can also be tweaked by using simple attribute-setting:

# set your own properties
feature.properties = {"newfield1":"newvalue1", "newfield2":"newvalue2"}

# borrow the geometry of the 16th feature
feature.geometry = testfile[16].geometry

Note that when changing geometries or coordinates, you must remember to update its bbox to clear away any older stored bbox information.

feature.geometry.update_bbox()

Constructing

Creating a new geojson file from scratch is also easy:

newfile = pygeoj.new()

# The data coordinate system defaults to long/lat WGS84 or can be manually defined:
newfile.define_crs(type="link", link="http://spatialreference.org/ref/epsg/26912/esriwkt/", link_type="esriwkt")

The new file can then be populated with new features:

newfile.add_feature(properties={"country":"Norway"},
                    geometry={"type":"Polygon", "coordinates":[[(21,3),(33,11),(44,22)]]} )
newfile.add_feature(properties={"country":"USA"},
                    geometry={"type":"Polygon", "coordinates":[[(11,23),(14,5),(66,31)]]} )

Finally, some useful additional information can be added to top off the geojson file before saving it to file:

newfile.add_all_bboxes()
newfile.update_bbox()
newfile.add_unique_id()
newfile.save("test_construct.geojson")

More Information:

License:

This code is free to share, use, reuse, and modify according to the MIT license, see license.txt

Credits:

  • Karim Bahgat
  • Mec-iS

Changes

1.0.0 (2018-09-13)

  • Bump to stable version
  • Officially support Python 3

0.2.5 (2017-02-19)

  • Fixed more robust validation to avoid unexpected errors
  • Added skiperror option
  • Fixed feat type missing when add_feature()
  • Fixed crs not saving
  • Added fixerror option when loading and validating
  • Fix bug to allow null geometries and empty properties, and correctly represent them in json as null

0.2.4 (2015-07-11)

  • Fixed bug with add_all_bboxes() not updating existing bboxes
  • Fixed bug with GeojsonFile bbox sometimes being calculated wrong.
  • Added update_bbox() on individual Geometry objects.

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