Installation

Topojson is available on PyPI and conda-forge:

pip install topojson

In a project managed with uv:

uv add topojson

Or with conda:

conda install -c conda-forge topojson

The library is installed successfully if the following code.

import topojson as tp

data = [
    {"type": "Polygon", "coordinates": [[[0, 0], [1, 0], [1, 1], [0, 1], [0, 0]]]},
    {"type": "Polygon", "coordinates": [[[1, 0], [2, 0], [2, 1], [1, 1], [1, 0]]]}
]

topo = tp.Topology(data, prequantize=False)
print(topo.to_json(pretty=True))

Returns something as such:

{
    "type": "Topology",
    "objects": {
        "data": {
            "geometries": [
                {"type": "Polygon", "arcs": [[-2, 0]], "id": 0},
                {"type": "Polygon", "arcs": [[1, 2]], "id": 1}
            ],
            "type": "GeometryCollection"
        }
    },
    "bbox": [0.0, 0.0, 2.0, 1.0],
    "arcs": [
        [[1.0, 0.0], [0.0, 0.0], [0.0, 1.0], [1.0, 1.0]], [[1.0, 0.0], [1.0, 1.0]],
        [[1.0, 1.0], [2.0, 1.0], [2.0, 0.0], [1.0, 0.0]]
    ]
}

Dependencies

Hard Dependencies

Topojson requires numpy and shapely. These are installed automatically if not available.

Soft Dependencies

For other simplification options in the presimplify/toposimplify parameter settings you can install (optional):

• simplification: Visvalingam-Whyatt, and a Douglas-Peucker that is quicker on long lines but does not prevent oversimplification.

For polygons, presimplify with simplify_with="geos" uses Visvalingam-Whyatt from shapely without this package, and keeps shared borders matched.

To visualize the output as a mesh and/or return the output as geodataframe you will need (optional):

• altair
• geopandas

To interactively analyze the effects of toposimplify and topoquantize as a widget, you also need (optional):

• ipywidgets

Development Install

To run the full test suite a few additional dependencies are required, next to the hard and soft dependencies:

• pytest
• geojson
• pyshp (to be able to do import shapefile)