`traitlets.traitlets:HasTraits.observe`

source: /traitlets/traitlets.py :1641

Signature

   def     observe (    self    ,    handler  :  t.Callable[..., t.Any]    ,    names  :  Sentinel | str | t.Iterable[Sentinel | str]    =  traitlets.All   ,    type  :  Sentinel | str    =  change     )   →  None

Summary

Setup a handler to be called when a trait changes.

Extended Summary

This is used to setup dynamic notifications of trait changes.

Parameters

handler : callable: A callable that is called when a trait changes. Its signature should be handler(change), where change is a dictionary. The change dictionary at least holds a 'type' key. * type: the type of notification. Other keys may be passed depending on the value of 'type'. In the case where type is 'change', we also have the following keys: * owner : the HasTraits instance * old : the old value of the modified trait attribute * new : the new value of the modified trait attribute * name : the name of the modified trait attribute.
names : list, str, All: If names is All, the handler will apply to all traits. If a list of str, handler will apply to all names in the list. If a str, the handler will apply just to that name.
type : str, All (default: 'change'): The type of notification to filter by. If equal to All, then all notifications are passed to the observe handler.

Aliases

traitlets.HasTraits.observe