def zpad(x, l):
    " Left zero pad value `x` at least to length `l`.\n\n    >>> zpad('', 1)\n    '\x00'\n    >>> zpad('Êþ', 4)\n    '\x00\x00Êþ'\n    >>> zpad('ÿ', 1)\n    'ÿ'\n    >>> zpad('Êþ', 2)\n    'Êþ'\n    "
    return b'\x00' * max(0, l - len(x)) + x
