Group by and count of a pandas dataframe column-CodePudding

I have a pandas dataframe where I am trying to group a column and get the unique values of another column.

  id    name   
  a-1   sfdad
  a-1   sfdad
  a-1   oiuoi
  a-2   oqrwq
  a-2   oqrwq
  a-2   ljlsg
  a-2   uoire

I do the group by using:

  df = df.groupby('id')['name'].agg(['unique'])
  df = df.reset_index()

and then when i do the count of column "unique" using the below statement, it does not align with the results of df['unique']. Length of df['unique'] and the below statement seems to be different.

 df.groupby('id')['name'].nunique()

Result

id   unique                count
a-1  [sfdad,oiuoi]         2
a-2  [oqrwq,ljlsg,uoire]   3

CodePudding user response：

You can compute several things at once with agg. This will necessarily be aligned:

df.groupby('id')['name'].agg(['unique', 'nunique'])

output:

                    unique  nunique
id                                 
a-1         [sfdad, oiuoi]        2
a-2  [oqrwq, ljlsg, uoire]        3