如何在 alt.color(condition=) 中使用 alt.condition()？

Question

I'm new to altair so i want to be able to see my code more clearly. that's why i'm trying to use long version coding. my problem is that, i could't find any documentation on how to use a alt.color(condition=) . How can i use condition= preferably with alt.condition() ?

brush = alt.selection_interval()

alt.Chart(cars).mark_point().encode(
    alt.Y("Horsepower"),
    alt.X("Miles_per_Gallon", title="consumption"),
    #alt.Tooltip(["Name", "Origin"]),
    #color=alt.condition(brush, 'Origin:N', alt.value('White')) I Know with this line my code will work 
    alt.Color(condition= alt.condition(brush,
                   alt.Color('Origin:N', legend=None),
                   alt.value('lightgray')))
).add_selection(
    brush
)

Answer 1

alt.condition is a shorthand for generating the full alt.Color specification for a conditional encoding. If you wish, you can create it more manually like this:

    alt.Color(
        condition={"selection": brush.name, "field": "Origin", "type": "nominal"},
        value='lightgray')

If you're really set on using alt.condition as an argument to condition= , you could do something like this:

    alt.Color(
        condition=alt.condition(brush, "Origin:N", "")["condition"],
        value='lightgray')

but it's a bit strange.