class Filename(bytes):
    def __new__(cls, filename, charset):
        obj = bytes.__new__(cls, filename)
        obj.characters = str(filename, charset, "replace")
        obj.charset = charset
        return obj

    def __str__(self):
        # str(Filename(filename, charset)) -> str(filename, charset, "replace")
        return self.characters

    def __add__(self, filename):
        # Filename(...) + 'text'
        newname = bytes.__add__(self, filename.encode(self.charset))
        return Filename(newname, self.charset)

    def __radd__(self, filename):
        # 'text' + Filename(...)
        newname = bytes.__add__(filename.encode(self.charset), self)
        return Filename(newname, self.charset)

    def __contains__(self, pattern):
        # 'pattern' in Filename(...)
        pattern = pattern.encode(self.charset)
        return bytes.__contains__(self, pattern)

    def startswith(self, pattern):
        # Filename(...).startswith('pattern')
        pattern = pattern.encode(self.charset)
        return bytes.startswith(self, pattern)

    def endswith(self, pattern):
        # Filename(...).endswith('pattern')
        pattern = pattern.encode(self.charset)
        return bytes.endswith(self, pattern)

    def index(self, pattern):
        # Filename(...).index('pattern')
        # Note: don't support start and end arguments
        pattern = pattern.encode(self.charset)
        return bytes.index(self, pattern)

    def __repr__(self):
        return "<Filename name={0} charset={1!r}>".format(bytes.__repr__(self), self.charset)

def test_listdir(path):
    from os import listdir
    from sys import getfilesystemencoding
    charset = getfilesystemencoding()
    for name in listdir(path):
        if isinstance(name, bytes):
            name = Filename(name, charset)
        yield name

if __name__ == "__main__":
    for name in test_listdir("/tmp/x"):
        print ("str={0}, repr={0!r}".format(name))