def unquote(s):
    """unquote('abc%20def') -> 'abc def'."""
    if _is_unicode(s):
        if '%' not in s:
            return s
        bits = _asciire.split(s)
        res = [bits[0]]
        append = res.append
        for i in range(1, len(bits), 2):
            append(unquote(str(bits[i])).decode('latin1'))
            append(bits[i + 1])
        return ''.join(res)

    bits = s.split('%')
    # fastpath
    if len(bits) == 1:
        return s
    res = [bits[0]]
    append = res.append
    for item in bits[1:]:
        try:
            append(_hextochr[item[:2]])
            append(item[2:])
        except KeyError:
            append('%')
            append(item)
    return ''.join(res)
unquote('abc%20def') -> 'abc def'.