Loading and Querying Datasets

Mundipy supports loading and querying any vector dataset supported by GDAL and tables from PostGIS. This includes Shapefiles, GeoJSON, FlatGeobufs, and KMLs, with a full list of drivers available here.

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Loading vector datasets

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Files from disk

Passing a filename as the first argument loads a vector file from disk:

from mundipy.dataset import Dataset

ds = Dataset('starbucks_in_seattle.shp')

print('Loaded %d coffeeshops' % len(ds))
# -> Loaded 308 coffeeshops

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Files over http/https

Mundipy will automatically download relevant parts of a remote file when you pass a URL:

from mundipy.dataset import Dataset

ds = Dataset('https://pub-f49c63ed10ee494eb0deeb568b66f33f.r2.dev/trails.fgb')

print('Loaded %d trails' % len(ds))
# -> Loaded 5885 trails

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PostGIS table

To download from a PostGIS table, pass the connection URL along with the table name:

from mundipy.dataset import Dataset

ds = Dataset({
    'url': "postgresql://postgres@localhost:5432/postgres",
    'table': 'nyc_boroughs'
})

print('Loaded %d boroughs' % len([ borough for borough in ds ]))
# -> Loaded 5 boroughs

If a loaded dataset is from PostGIS or is a Shapefile or FlatGeobuf, we can use the spatial index to query a subset of the data.

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Querying datasets

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Intersection

We can get a list of geometries that intersect with a given geometry by using ds.intersects(geom).

intersects = ds.intersects(geom)

print(intersects)
# [<mundipy.geometry.Point object at 0x10e4f8160>, <mundipy.geometry.Point object at 0x10e435fc0>, <mundipy.geometry.Point object at 0x1115c1720>]

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Nearest

This returns the geometry that is closest to the given geometry. Useful for nearest neighbor queries.

Returns None if the dataset is empty.

pt = ds.nearest(geom)

print(pt)
# <mundipy.geometry.Point object at 0x10e4f8160>

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Within

Returns a list of geometries that fall within a certain radius of the given geometry.

Useful for finding all of the points of interest near an area. Geometry does not have to be a Point.

pois_in_walking_distance = ds.within(1200, geom)

print(pois_in_walking_distance)
# [<mundipy.geometry.Point object at 0x10e4f8160>, <mundipy.geometry.Point object at 0x10e435fc0>]

This is equivalent to calling ds.intersects(geom.buffer(1200)).