def list_zfill(l, width):
    """
    Pad a list with empty strings on the left, to fill the list to the
    specified width.  No-op when len(l) >= width.

    >>> list_zfill(['a', 'b'], 5)
    ['', '', '', 'a', 'b']
    >>> list_zfill(['a', 'b', 'c'], 1)
    ['a', 'b', 'c']
    >>> list_zfill(['a', 'b', 'c'], 3)
    ['a', 'b', 'c']
    """
    list_len = len(l)
    if len(l) >= width:
        return l

    return [ '' for _ in range(0, width-list_len) ] + l