Extension without sub-classing?

[Martin d'Anjou]

Is it possible to extend a python class without sub-classing?

For example, in file1.py

class car:
    def start_engine(self):
       print "Started"

And in file2.py, continue the declaration of the car class, without specializing 
  it:

extend car:
    def apply_breaks(self):
       print "You have stopped"

I know the "extend" syntax is wrong, but I want to extend "car" without 
sub-classing. Is this possible and how?

Thanks,
M.