`traitlets.traitlets:directional_link`

Signature

   class     directional_link (    source  :  t.Any    ,    target  :  t.Any    ,    transform  :  t.Any    =  None     )   →  None

Link the trait of a source object with traits of target objects.

source : (object, attribute name) pair
target : (object, attribute name) pair
transform: callable (optional): Data transformation between source and target.

class X(HasTraits):
    value = Int()

src = X(value=1)
tgt = X(value=42)
c = directional_link((src, "value"), (tgt, "value"))

Setting source updates target objects:

src.value = 5
tgt.value

Setting target does not update source object:

tgt.value = 6
src.value