Tal: If you want to verify your is_id_char function, you could use the code for i in range(65536): c = chr(i) c2 = 'a'+c if is_id_char(c) != c2.isidentifier(): print('\\u%.4x'%i,is_id_char(c),c2.isidentifier()) Alternatively, you could use the strategy taken in that code for is_id_char itself: def is_id_char(c): return ('a'+c).isidentifier()