基于嵌套范围的指针向量循环

Question

我有一个 year | brand | total money earned 2018 nike 5000000000 2018 adidas 498000000 2019 nike 30000000000 ，类型为albumCollection。我的vector<Album*>类又拥有一个Album。效果很好：

vector<Track*>

但是尝试一下：

for(Album* i : albumCollection) {
    cout << i;
}

我得到了错误：

for(Album* i : albumCollection) { for (Track* j : i) { cout << j; } }

和：

no callable 'begin' function found for type 'Album *'

Answer 1

您需要每个# Create an empty dataframe with column names dffinal = pd.DataFrame(columns=['parent','child','numeric_result_list']) # Group by 'parent' and 'child' parent_child = df2.groupby(['parent', 'child']) i = 1 for name, group in parent_child: print('Processing: ', name) group = group.reset_index(drop=True) _array2d_ = make2dList(rows, cols) _array2d_ = modify2dlist(_array2d_, _group_) dffinal.loc[i] = [name[0], name[1], _array2d_] i = i+1 print('done') dff = dff.reset_index(drop=True) 中包含的向量在嵌套循环中的Limitations的右侧。看起来像

Album