ipygis

A bridge to GIS libraries running in the browser.

Development installation

micromamba create -n ipygis
micromamba activate ipygis
micromamba install xeus-python pip "nodejs<25"
pip install jupyterlab -e .
jupyter labextension develop --overwrite .

When making changes to the JavaScript code, you can just recompile that part:

jlpm run build

Running the example notebooks

Run examples/build_time.ipynb first to create the Icechunk repository. This notebook cannot run in JupyterLite because of incompatible libraries, but the created repository is the only thing that will be needed by examples/run_time.ipynb.

That notebook uses a read-only API modeled on Zarr-Python’s asynchronous interface. Zarrita reads, decodes, and slices arrays in the browser, returning NumPy arrays to Python without Zarr-Python’s synchronous bridge. The browser uses icechunk-js by default. This backend requires no COOP/COEP headers or shared memory. You can change the backend to "@earthmover/icechunk" but this is a WASM library that needs SharedArrayBuffer and so the server must send COOP/COEP headers. In this case JupyterLab must use a special configuration:

jupyter lab --config=./jupyter_server_config.json

Both readers are installed from npm. No local Icechunk checkout or WASM preparation step is required. The published @earthmover/icechunk 2.0.3 package does not include the browser HTTP virtual-chunk callback; use backend="icechunk-js" for the HydroSHEDS runtime notebook.

Asynchronous array reads

from ipygis.zarr import asynchronous as zarr

group = await zarr.open_group(session.store, mode="r")
array = await group.getitem("0")
print(array.shape, array.dtype, array.chunks)
region = await array.getitem((10, slice(100, 200), slice(200, 300)))
point = await array.getitem((10, 100, 200))

You can also use await zarr.open_array(session.store, path="0", mode="r"). Reads support integers (including negative indices), ellipses, and positive-step slices. Integer and floating-point dtypes from 8-bit integers through 64-bit integers/floats are supported; 64-bit integers are transferred as binary data. Point selections return NumPy scalars; other selections return NumPy arrays. Metadata attributes are local snapshots, not a write API. Writing, fancy/boolean indexing, new axes, negative slice steps, and nonnumeric dtypes are unsupported. TIFF LZW decoding is registered in JavaScript automatically. Other codecs must be supported by Zarrita; this API does not apply xarray's CF decoding or geospatial coordinate selection. Close the session after finishing all reads.

The existing session.store remains usable with Zarr-Python. The new array API uses its browser backend directly; Python does not fetch or decode the chunks.