Include vl-convert-python as a dependency of Altair?

[mattijn]

Lets open this issue. Title says it all. What are the cons and pros?

Pros:

• easy to save charts to file, svg/png
• other libraries also come included with saving engines

Cons:

• 20mb

[jonmmease]

In general, I don't think it's a good idea for a pure Python library like Altair to have a hard dependency on a native library if it can be avoided. This would break the use of Altair in contexts where vl-convert-python isn't pre-compiled. One notable example would be pyodide/pyscript. But also various arm architectures that are pre-built yet.

We could add vl-convert-python to an extra_require group and then update the docs to install using that group. For example, we could add vl-convert-python, altair-viewer, and vega-datasets to an extra_require group named full and then instruct people in the docs to install altair with

pip install "altair[full]"

[mattijn]

That sounds good to me 👍.

[mattijn]

Thanks @jonmmease for your comment and idea: closed in favor of #2818.