Pandas中中括号和双中括号

来源：互联网发布：jre 源码编辑：程序博客网时间：2024/05/23 16:15

当我们使用pandas中的groupby进行分组聚合时，若对需要聚合的单列使用双中括号，则输出时会带有列标签

df.groupby(['key1','key2'])[['data2']].mean()Out[27]:               data2key1 key2          a    one   0.072958     two  -0.962946b    one   0.946299     two   1.576233

若对需要聚合的单列使用单中括号，则输出时不会带有列标签，末尾会单独输出一行属性列

df.groupby(['key1','key2'])['data2'].mean()Out[29]: key1  key2a     one     0.072958      two    -0.962946b     one     0.946299      two     1.576233Name: data2, dtype: float64

若需要将多列进行聚合时，单中括号和双中括号没有区别

df.groupby(['key1','key2'])['data1','data2'].mean()Out[31]:               data1     data2key1 key2                    a    one   0.018737  0.072958     two  -1.319022 -0.962946b    one   0.917741  0.946299     two  -1.288477  1.576233

df.groupby(['key1','key2'])[['data1','data2']].mean()Out[30]:               data1     data2key1 key2                    a    one   0.018737  0.072958     two  -1.319022 -0.962946b    one   0.917741  0.946299     two  -1.288477  1.576233

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