按多列取消分组的熊猫数据框

Question

I have a pandas_dataframe like this.

df=pd.DataFrame({'name':['A','A','B','C','B','B','C','C','C','A'],'ids':['M_1','M_1','K_1','K_1','K_1','K_1','G_1','G_1','G_1','K_1'],
            'no' :[1,2,1,2,3,1,2,3,4,1],'colors':['Red','black','green','blue','yellow','white','rose','pink','maroon','lightblue']})
          

The data frame after sorted by name and ids looks like this.

After grouping by name and ids, it looks like this. I want the final data frame with a new column and ungrouped. I am new to this forum and yet to learn how to paste the outputs obtained from jupyter notebook.

Answer 1

Try with transform

df['max_no'] = df.groupby(['name','ids'])['no'].transform('max')
df
Out[147]: 
  name  ids  no     colors  max_no
0    A  M_1   1        Red       2
1    A  M_1   2      black       2
2    B  K_1   1      green       3
3    C  K_1   2       blue       2
4    B  K_1   3     yellow       3
5    B  K_1   1      white       3
6    C  G_1   2       rose       4
7    C  G_1   3       pink       4
8    C  G_1   4     maroon       4
9    A  K_1   1  lightblue       1