def strip(table, col):
    """Removes column col from the given table
    Preconditions: table is a (non-ragged) 2d List,
    col valid column"""
    n_row = len(table)
    n_col = len(table[0])
    assert col < n_col, repr(col) + "要删除的列大于总列数！"
    for row in range(n_row):
        table[row] = table[row][:col]+table[row][col+1:]
    # print(table)
    return table