Create columns from row with same ID

问题

I have a df like this:

Id      username  age

1       michael.     34
6.      Mike.          65
7.      Stephanie.  14
1.      Mikael.        34
6.      Mick.           65

As you can see, username are not writed the same for the same id. I would like to regroup all username to the same row like this:

Id      username      username_2    Age

1       michael.         mikael.           34
6.      Mike.             Mick.              65
7.      Stephanie.                           14

Thanks.

回答1:

You can create MultiIndex for count duplicated Id by cumcount and then is possible reshape by unstack, last some data cleaning by add_prefix with reset_index:

df1 = (df.set_index(['Id', df.groupby('Id').cumcount()])['username']
         .unstack(fill_value='')
         .add_prefix('username_')
         .reset_index())
print (df1)
    Id username_0 username_1
0  1.0    michael     Mikael
1  6.0       Mike       Mick
2  7.0  Stephanie           

Or rename columns for start from 1:

df1 = (df.set_index(['Id', df.groupby('Id').cumcount()])['username']
         .unstack(fill_value='')
         .rename(columns = lambda x: f'username_{x+1}')
         .reset_index())
print (df1)
    Id username_1 username_2
0  1.0    michael     Mikael
1  6.0       Mike       Mick
2  7.0  Stephanie        

来源：https://stackoverflow.com/questions/54802003/create-columns-from-row-with-same-id