howto overload with a NOP (empty statement)

[Stef Mientki]

How should I overload / disable a method ?
In the example below I have defined the class "Power_Supply", derived 
from baseclass "device".
The baseclass has a method "execute", which will be implemented in most 
derived classes, but not in all.
Now apparently it's not allowed to overload a method with an empty 
statement.
I could write a nonsense dummy statement, like "A= 3", but isn't there 
another way ?

thanks, Stef Mientki

class device:
   def execute (self):
     print 'execute not yet implemented for', self.Name


class Power_Supply (device):
   def execute (self): ;