def is_ascii(str_):
    if sys.version_info.major < 3:
        try:
            str_.decode('ascii')
            return True
        except UnicodeEncodeError:
            return False
    elif sys.version_info.major == 3 and sys.version_info.minor < 7:
        try:
            str_.encode('ascii')
            return True
        except UnicodeEncodeError:
            return False:
    else:
        return str_.isascii()