def assertIsNot(first, second, msg=''):
 (a, b) = (first, second)
 assert (a is not b), ('%s: %r is %r' % (msg.format(a, b), a, b))

def assertIsNot ( first , second , msg = '' ) : ( a , b ) = ( first , second ) assert ( a is not b ) , ( '%s: %r is %r' % ( msg . format ( a , b ) , a , b ) )
checks that first is not second .