`traitlets.traitlets:HasTraits.on_trait_change`

source: /traitlets/traitlets.py:1642

Signature

def on_trait_change(self, handler: EventHandler | None = None, name: Sentinel | str | None = None, remove: bool = False) → None

Summary

DEPRECATED: Setup a handler to be called when a trait changes.

Extended Summary

This is used to setup dynamic notifications of trait changes.

Static handlers can be created by creating methods on a HasTraits subclass with the naming convention '_[traitname]_changed'. Thus, to create static handler for the trait 'a', create the method _a_changed(self, name, old, new) (fewer arguments can be used, see below).

If remove is True and handler is not specified, all change handlers for the specified name are uninstalled.

Parameters

handler : callable, None: A callable that is called when a trait changes. Its signature can be handler(), handler(name), handler(name, new), handler(name, old, new), or handler(name, old, new, self).
name : list, str, None: If None, 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.
remove : bool: If False (the default), then install the handler. If True then unintall it.

Aliases

traitlets.HasTraits.on_trait_change