def _lpad(self, length, pad=' '):
    """
    Returns string of given length by truncating (on right)
    or padding (on left) original string

    Parameters
    ----------
    length : int
    pad : string, default is ' '

    Examples
    --------
    >>> import ibis
    >>> table = ibis.table([('strings', 'string')])
    >>> expr = table.strings.lpad(5, '-')
    >>> expr = ibis.literal('a').lpad(5, '-')  # 'a' becomes '----a'
    >>> expr = ibis.literal('abcdefg').lpad(5, '-')  # 'abcdefg' becomes 'abcde'  # noqa: E501

    Returns
    -------
    padded : string
    """
    return ops.LPad(self, length, pad).to_expr()