The core Python API for Altair can be found in the following locations:
altair/vegalite/v5/schema/
All the files within these directories are created automatically by running the following script from the root of the repository:
hatch run generate-schema-wrapper
This script does a couple things:
- downloads the appropriate schema files from the specified vega-lite
release versions & copies the JSON file to the appropriate
schema
directory - generates basic low-level schemapi wrappers from the definitions within
the schema: this is put in the
schema/core.py
file - generates a second layer of higher level wrappers for some vega-lite
functionality; this is put in
schema/channels.py
andschema/mixins.py
The script output is designed to be deterministic; if the vega-lite version is not changed, then running the script should overwrite the schema wrappers with identical copies.
The vega & vega-lite versions for the Python code can be updated by manually
changing the SCHEMA_VERSION
definition within
tools/generate_schema_wrapper.py
, and then re-running the script.
This will update all of the automatically-generated files in the schema
directory for each version, but please note that it will not update other
pieces (for example, the core of the Altair API, including methods and
doc strings within altair/vegalite/v5/api.py
).
These additional methods have fairly good test coverage, so running the test
suite should identify any inconsistencies:
hatch test
Generally, minor version updates (e.g. Vega-Lite 2.3->2.4) have been relatively painless, maybe requiring the addition of a few chart methods or modification of some docstrings. Major version updates (e.g. Vega-Lite 1.X->2.X) have required substantial rewrites, because the internal structure of the schema changed appreciably.
To update the Vega-Lite version used in JupyterChart, update the version in the
esm.sh URL in altair/jupyter/js/index.js
.
For example, to update to Vega-Lite 5.15.1, Vega 5 and Vega-Embed 6, the URL should be:
import embed from "https://esm.sh/vega-embed@6?deps=vega@5&[email protected]";
When updating the version of Vega-Lite, it's important to ensure that
vl-convert includes support for the new Vega-Lite version.
Check the vl-convert releases to find the minimum
version of vl-convert that includes support for the desired version of Vega-Lite (and open
an issue if this version hasn't been
included in a released yet.). Update the vl-convert version check in altair/utils/_importers.py
with the new minimum required version of vl-convert.
Also, the version bound of the vl-convert-python
package should be updated in the
[project.optional-dependencies]/all
dependency group in pyproject.toml
.
To cut a new release of Altair, follow the steps outlined in RELEASING.md.
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