unset onkeydown for a key?

[Josh]

Thanks so far...

The space bar should only be pressed once in my experiment:

vizact.onkeydown(' ', play_first_joke)

As soon as it's been pressed, it shouldn't invode the play_first_joke method anymore.

vizact.onkeydown(' ', None)

...gives the following error:

Traceback (most recent call last):
  File "C:\Programme\WorldViz\Vizard30\python\vizact.py", line 3019, in __onkeydown
    self._callGroup(self.__keydownmap[key])
  File "C:\Programme\WorldViz\Vizard30\python\vizact.py", line 2971, in _callGroup
    val = e.call(arg)
  File "C:\Programme\WorldViz\Vizard30\python\vizact.py", line 2794, in _callStatic
    return func(*args,**kwargs)
TypeError: 'NoneType' object is not callable