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Functions to read and write data

Functions to read and write data

pyst supports most of the common geospatial formats, including geoJSON and WKT.

GeoJSON format

To work with files in geoJSON format in a Python notebook, first create a geoJSON reader and writer:

geojson_reader = stc.geojson_reader()
geojson_writer = stc.geojson_writer()

The following code snippets show reading live location data in geoJSON format available in Mapbox:

  • Read the contents of a GeoJSON file copied to your local machine from Mapbox and display the first three lines of the file:
    ! wget -q https://www.mapbox.com/help/data/stations.geojson
df = geojson_reader.read('stations.geojson')
df.head(3)
  • Read content in GeoJSON format from a Python dictionary:
    data = json.load(open('stations.geojson'))
df = geojson_reader.read(data)
df.head(3)
  • Read data directly from Mapbox by using a URL and display the first three lines of the file:
    df = geojson_reader.read(‘https://www.mapbox.com/help/data/stations.geojson’) df.head(3)
  • Read binary data (useful when reading streaming bytes from IBM Cloud Object Storage for example):
    # Assume station.geojson is in IBM Cloud Object Storage in the bucket "test"
client = ibm_boto3.client('s3')
streaming_body_2 = client.get_object(Bucket='test', Key='station.geojson')['Body']
df = shapefile_reader.read(streaming_body_2.read())
df.head(3)
  • Write the contents in a pandas DataFrame to a Python dictionary:
    geojson_writer.write(df)
  • Write the contents of a pandas DataFrame to a GeoJSON file:
    geojson_writer.write(df, file_name='stations_out.geojson')

WKT strings

To work with WKT strings in a Python notebook, first create a WKT reader and writer:

wkt_reader = stc.wkt_reader()
wkt_writer = stc.wkt_writer()

The following code snippets show reading from and writing to a WKT string:

  • Read a WKT string to a geometry object:
    >>> westchester_WKT = 'POLYGON((-73.984 41.325,-73.948 41.33,-73.78 41.346,-73.625 41.363,-73.545 41.37,-73.541 41.368,-73.547 41.297,-73.485 41.223,-73.479 41.215,-73.479 41.211,-73.493 41.203,-73.509 41.197,-73.623 41.144,-73.628 41.143,-73.632 41.14,-73.722 41.099,-73.714 41.091,-73.701 41.073,-73.68 41.049,-73.68 41.047,-73.673 41.041,-73.672 41.038,-73.668 41.035,-73.652 41.015,-73.651 41.011,-73.656 41,-73.655 40.998,-73.656 40.995,-73.654 40.994,-73.654 40.987,-73.617 40.952,-73.618 40.946,-73.746 40.868,-73.751 40.868,-73.821 40.887,-73.826 40.886,-73.84 40.89,-73.844 40.896,-73.844 40.9,-73.85 40.903,-73.853 40.903,-73.854 40.9,-73.859 40.896,-73.909 40.911,-73.92 40.912,-73.923 40.914,-73.923 40.918,-73.901 40.979,-73.894 41.023,-73.893 41.043,-73.896 41.071,-73.894 41.137,-73.94 41.207,-73.965 41.24,-73.973 41.244,-73.975 41.247,-73.976 41.257,-73.973 41.266,-73.95 41.288,-73.966 41.296,-73.98 41.309,-73.984 41.311,-73.987 41.315,-73.987 41.322,-73.984 41.325))'
>>> westchester = wkt_reader.read(westchester_WKT)
>>> westchester.area()
1363618331.5760047
>>> westchester.centroid()
Point(41.15551622739597, -73.7592843233704)
>>> westchester.get_bounding_box()
BoundingBox: Lower Corner: Point(40.86800000000001, -73.987), Upper Corner: Point(41.36999999999998, -73.479)
  • Write a geometry object to a WKT string:
    >>> wkt_writer.write(westchester)
'POLYGON ((-73.984 41.325, -73.987 41.322, -73.987 41.315, -73.984 41.311, -73.98 41.309, -73.966 41.296, -73.95 41.288, -73.973 41.266, -73.976 41.257, -73.975 41.247, -73.973 41.244, -73.965 41.24, -73.94 41.207, -73.894 41.137, -73.896 41.071, -73.893 41.043, -73.894 41.023, -73.901 40.979, -73.923 40.918, -73.923 40.914, -73.92 40.912, -73.909 40.911, -73.859 40.896, -73.854 40.9, -73.853 40.903, -73.85 40.903, -73.844 40.9, -73.844 40.896, -73.84 40.89, -73.826 40.886, -73.821 40.887, -73.751 40.868, -73.746 40.868, -73.618 40.946, -73.617 40.952, -73.654 40.987, -73.654 40.994, -73.656 40.995, -73.655 40.998, -73.656 41.0, -73.651 41.011, -73.652 41.015, -73.668 41.035, -73.672 41.038, -73.673 41.041, -73.68 41.047, -73.68 41.049, -73.701 41.073, -73.714 41.091, -73.722 41.099, -73.632 41.14, -73.628 41.143, -73.623 41.144, -73.509 41.197, -73.493 41.203, -73.479 41.211, -73.479 41.215, -73.485 41.223, -73.547 41.297, -73.541 41.368, -73.545 41.37, -73.625 41.363, -73.78 41.346, -73.948 41.33, -73.984 41.325))'

Direct Input

Besides reading geometry objects from different sources, direct input is also supported and each geometry type comes with a constructor:

  • Point: point(lat, lon)
  • LineSegment: line_segment(start_point, end_point)
  • LineString: line_string([point_1, point_2, …]) or line_string([line_segment_1, line_segment_2, …])
  • Ring: ring([point_1, point_2, …]) or ring([line_segment_1, line_segment_2, …])
  • Polygon: polygon(exterior_ring, [interior_ring_1, interior_ring_2, …])
  • MultiGeometry: multi_geometry(geom_1, geom_2, …)
  • MultiPoint: multi_point(point_1, point_2, …)
  • MultiLineString: multi_line_string(line_string_1, line_string_2, …)
  • MultiPolygon: multi_polygon(polygon_1, polygon_2, …)
  • Null Geometry: null_geometry()
  • FullEarth: full_earth()
  • BoundingBox: bounding_box(lower_lat, lower_lon, upper_lat, upper_lon)

Some examples:

point_1 = stc.point(37.3, -74.4)
point_2 = stc.point(37.5,-74.1)
point_3 = stc.point(38.1, -74.4)
line_segment = stc.line_segment(point_1, point_2)
line_string = stc.line_string([point_1, point_2, point_3])
ring = stc.ring([point_1, point_2, point_3, point_1])
poly = stc.polygon(ring)
multi_points = stc.multi_point([point_1, point_2, point_3])

>>> poly.area()
1179758985.44891
>>> multi_points
MultiPoint(Point(37.5, -74.1), Point(38.1, -74.4), Point(37.3, -74.4))
>>> next(multi_points)
Point(37.5, -74.1)
>>> next(multi_points)
Point(38.1, -74.4)
>>> next(multi_points)
Point(37.3, -74.4)