python 2.7 - Custom events in Tkinter -

i new in tkinter.
, want know there way catch custom events widgets,
example catch on_packed event after widget.pack() or on_paint event canvas widget after drawing graphics on canvas, etc?

the events describe don't exist. can use widgets event_generate method create own custom events if wish. create own widget classes emit custom events want.

in specific case of on_pack, there events want @ more abstract level. example, there events fire when widget becomes visible, changes size, etc.