is_surrogate.py

def is_surrogate(string):
    for index, char in enumerate(string):
        if 0xD800 <= ord(char) <= 0xDBFF:
            try:
                next_char = string[index + 1]
            except IndexError:
                pass
            if 0xDC00 <= ord(next_char) <= 0xDFFF:
                return True
            else:
                raise ValueError(u"Illegal UTF-16 sequence: {}".format(string))
    return False