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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

So far only tested on Python version 2.x.

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 “C:/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")

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.common_attributes # retrieves which field attributes 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

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.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 (2015)

Project details


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