如何取消选择 Altair 的下拉框

Question

My question is about the drop down box of Altair (Python's visualization library).

In this example in the official document, you can select the country of origin of cars. If you select one, then only the selected instances remain the same (or have the original color) and the other instances are grayed out.

My question is: How can I cancel the selection? Or is it possible to customize the code so that the drop box has the option for de-select?

Answer 1

You can change

input_dropdown = alt.binding_select(options=['Europe','Japan','USA'])

to

input_dropdown = alt.binding_select(options=[None,'Europe','Japan','USA'],labels=['All','Europe','Japan','USA'])

This will add 'All' as an option in your drop-down. Clicking on it de-selects your previous selection.