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https://github.com/fortyninemaps/picogeojson
Compliant GeoJSON
https://github.com/fortyninemaps/picogeojson
geojson python
Last synced: 3 months ago
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Compliant GeoJSON
- Host: GitHub
- URL: https://github.com/fortyninemaps/picogeojson
- Owner: fortyninemaps
- License: mit
- Created: 2016-12-29T04:49:30.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2022-06-05T20:12:08.000Z (over 2 years ago)
- Last Synced: 2024-05-19T23:36:50.619Z (6 months ago)
- Topics: geojson, python
- Language: Python
- Homepage:
- Size: 133 KB
- Stars: 13
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG
- License: LICENSE
Awesome Lists containing this project
README
# picogeojson
[](https://travis-ci.org/fortyninemaps/picogeojson)
[](https://coveralls.io/github/fortyninemaps/picogeojson?branch=master)
# picogeojson
*picogeojson* is a Python library for reading, writing, and working with
GeoJSON. It emphasizes standard compliance ([RFC
7946](https://tools.ietf.org/html/rfc7946)) and ergonomics. It is a pure-Python
module for ease of installation and distribution.
## Encoding and Decoding
GeoJSON files or strings are read using `fromstring()`, `fromfile()`, or
`fromdict()`.
```python
picogeojson.fromstring('{"type": "Point", "coordinates": [1.0, 3.0]}')
# ->
```
GeoJSON objects are serialized with `tostring()`, `tofile()`, or `todict()`.
```python
picogeojson.tostring(
picogeojson.Point([1.0, 3.0])
)
# -> {"coordinates": [1.0, 3.0], "type": "Point"}'
```
All of the serialization functions accept the following options:
**`antimeridian_cutting`**: *bool*: Cuts geometries at the 180th meridian so
that they plot well on standard world maps.
**`write_bbox`**: *bool*: Write an optional `bbox` member to the GeoJSON object.
**`write_crs`**: *bool*: Write a non-standard `crs` member for non-WGS84
longitude-latitude coordinates.
**`precision`**: *int*: Restrict the number of decimal digits in the written
coordinates (5 results in precision of 1 meter or better for longitude-latitude
coordinates).
When reading GeoJSON, *picogeojson* returns a *Map* object, which is a container
for GeoJSON. Useful methods on *Map* objects include:
**`Map.extract(geotype)`**: creates a generator for geometries of type
*geotype*, as in
```python
geojson = picogeojson.loads(...)
for linestring in geojson.extract(picogeojson.LineString):
print(linestring)
```
**`Map.extract_features(geotype=None, properties=None)`**: similar to
`Map.extract`, this extract GeoJSON features, optionally filtering by
properties.
```python
geojson = picogeojson.loads(...)
for lake in geojson.features("Polygon", {"type": "Lake", "state": "Oregon"}):
lakes_in_oregon.append(lake)
```
**`Map.map(function, geotype)`**: returns a new `Map` with *function* applied to
every contained GeoJSON geometry of type *geotype*.
**`Map.map_features(function, geotype)`**: returns a new `Map` with *function*
applied to every contained GeoJSON feature containing geometry *geotype* and
matching *properties*.
## Types and transformations
In order to create or work with GeoJSON, *picogeojson* defines constructors for
all GeoJSON types:
```python
pt = picogeojson.Point([1.0, 3.5])
polygon = picogeojson.Polygon([[[100.0, 20.0], [102.0, 19.7], [102.3, 23.0],
[100.1, 22.8], [100.0, 20.0]]])
feature = picojson.Feature(polygon, {"id": "example polygon"})
```
When constructing geometries, *picogeojson* takes care of ensuring that
coordinate rings are closed and oriented correctly and that coordinates are
nested to the correct depth.
The following methods are available:
| Type | `.transform` | `.map` | `.flatmap` |
|--------------------|--------------|--------|------------|
| Point | x | - | - |
| LineString | x | - | - |
| Polygon | x | - | - |
| MultiPoint | x | - | - |
| MultiLineString | x | - | - |
| MultiPolygon | x | - | - |
| GeometryCollection | x | x | x |
| Feature | x | x | - |
| FeatureCollection | x | x | x |
**`.transform`** operates on coordinates, returning a new geometry or feature
with a function applied to each coordinate pair.
**`.map`** applies a function to each member of a *GeometryCollection* or
*FeatureCollection*. *Feature*s have a `.map_geometry` and a `.map_properties`
that apply functions to the underlying geometry or properties dict,
respectively.
**`.flatmap`** applies a function to each member of a collection, constructing a
new collection by concatenating the result of each application.
## Miscellaneous
GeoJSON objects may be composed (`merge()`) or split (`burst()`).
```python
points = [picogeojson.Point((1, 2)),
picogeojson.Point((3, 4)),
picogeojson.Point((5, 6))]
merged_points = picogeojson.merge(points)
# -> MultiPoint(coordinates=[(1, 2), (3, 4), (5, 6)])
split_points = picogeojson.burst(merged_points)
# -> [Point((1, 2)), Point((3, 4)), Point((5, 6))]
```
## Performance
*The following benchmarks are old and likely inaccurate.*
*picogeojson* relies on [ujson](https://pypi.org/project/ujson/).
The read benchmark involves reading a list of earthquake features. The write
benchmark involves serializing the continent of Australia.
|Module |Read |Write |
|------------|-------|-------|
|json |1.49 |2.00 |
|geojson |6.74 |same |
|picogeojson |1.63 |0.31\* |
\*antimeridian cutting and polygon winding check set to `False`