def add_driver(key, driver_class, force=False):
 try:
  drivers[key]
  if (not force):
   raise ValueError, ('A DB driver named "%s" is already installed' % key)
 except KeyError:
  pass
 drivers[key] = driver_class

def add_driver ( key , driver_class , force = False ) : try : drivers [ key ] if ( not force ) : raise ValueError , ( 'A DB driver named "%s" is already installed' % key ) except KeyError : pass drivers [ key ] = driver_class
add a driver class to the list of drivers .