TraitsUI CheckListEditor with default selections?

Question

I'm using a CheckListEditor (source, docs) to present a list of options to users for configuring a simulation. By using the custom View options, it displays these selections as checkboxes. What I can't figure out is how to set some pre-selected or pre-checked boxes? IE the default settings for the simulation.

from traits.api import *
from traitsui.api import *

class Test(HasTraits):          
    foo = List(editor=CheckListEditor(values = ['a','b','c']))

    traits_view = View(Item('foo', style='custom'))

Test().configure_traits()

Below is a SS of the output. How would I initialize this with say a and b checked?

Thanks.

Answer 1

One way is to specify the default value of the List. That is, change this:

    foo = List(editor=CheckListEditor(values = ['a','b','c']))

to

    foo = List(editor=CheckListEditor(values = ['a','b','c']), value=['a', 'b'])