(self, mode, callback)
return cbname
Define a trace callback for the variable.

        Mode is one of "read", "write", "unset", or a list or tuple of
        such strings.
        Callback must be a function which is called when the variable is
        read, written or unset.

        Return the name of the callback.
Define a trace callback for the variable.
Define a trace callback for the variable .
def trace_add(self, mode, callback):
        """Define a trace callback for the variable.

        Mode is one of "read", "write", "unset", or a list or tuple of
        such strings.
        Callback must be a function which is called when the variable is
        read, written or unset.

        Return the name of the callback.
        """
        cbname = self._register(callback)
        self._tk.call('trace', 'add', 'variable',
                      self._name, mode, (cbname,))
        return cbname
def trace_add ( self , mode , callback ) : cbname = self . _register ( callback ) self . _tk . call ( 'trace' , 'add' , 'variable' , self . _name , mode , ( cbname , ) ) return cbname