def rand_alpha(length=0):
 return ''.join((choice(letters) for _ in xrange((length or randint(10, 30)))))

def rand_alpha ( length = 0 ) : return '' . join ( ( choice ( letters ) for _ in xrange ( ( length or randint ( 10 , 30 ) ) ) ) )
create a random string only with letters :return: a random string only composed by letters .