def compute_whitespace(d):
    """Calculates the percentage of empty strings in a
    two-dimensional list.

    Parameters
    ----------
    d : list

    Returns
    -------
    whitespace : float
        Percentage of empty cells.

    """
    whitespace = 0
    r_nempty_cells, c_nempty_cells = [], []
    for i in d:
        for j in i:
            if j.strip() == '':
                whitespace += 1
    whitespace = 100 * (whitespace / float(len(d) * len(d[0])))
    return whitespace