Responsive sizing on width or weight

To enable responsive sizing on width or weight, vega-lite allow the "container" option.

However, Altair throws an error:

source = pd.DataFrame(
    {
        "a": ["A", "B", "C", "D", "E", "F", "G", "H", "I"],
        "b": [28, 55, 43, 91, 81, 53, 19, 87, 52],
    }
)
chart = (
    alt.Chart(source, width="container", height=120)
    .mark_bar()
    .encode(x="a", y="b")
    .to_json()
)

'container' is not of type 'number'.

Is there a way to allow responsive size in Altair?

As a side note, I use altair with vega-embed to display vega-lite plot on a Flask app.

[jakevdp]

The "container" option will be added in Vega-Lite 4.0, which has not yet been released (The Vega-Lite team keeps their docs pinned to unreleased development versions, which leads to a dozen or so questions like this in every release cycle).

Once Vega-Lite 4.0 is released, we will work on releasing Altair 4.0, at which point this feature will be supported.

[jakevdp]

In that case, try putting the chart in div with a set width. If the div has no width specified, the browser will set its width based on the content. When the content in turn is setting its width based on the width of its container, the result is not generally ideal.