idlelib.HyperParser.Hyperparser has these lines
    _whitespace_chars = " \t\n\\"
    _id_chars = string.ascii_letters + string.digits + "_"
    _id_first_chars = string.ascii_letters + "_"
used in _eat_identifier() and get_expression. At least the latter two should be turned into functions that access the unicode datebase. (Such functions, if not already present in the stdlib, should be. But adding something elsewhere would be another issue.)