Need a cumsum of each name in a single column-CodePudding

I need a cumulative sum of each name in my df['Name'] column, but I need the count to reset when a new name appears in the column. How would I accomplish this in pandas? I've tried various things with df.cumsum, df.rolling, etc with no luck.

Name
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Devonta Freeman
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown
Antonio Brown

Desired Output:

Name    Count
Devonta Freeman 1
Devonta Freeman 2
Devonta Freeman 3
Devonta Freeman 4
Devonta Freeman 5
Devonta Freeman 6
Devonta Freeman 7
Devonta Freeman 8
Devonta Freeman 9
Devonta Freeman 10
Devonta Freeman 11
Devonta Freeman 12
Devonta Freeman 13
Devonta Freeman 14
Devonta Freeman 15
Antonio Brown   1
Antonio Brown   2
Antonio Brown   3
Antonio Brown   4
Antonio Brown   5
Antonio Brown   6
Antonio Brown   7
Antonio Brown   8
Antonio Brown   9
Antonio Brown   10
Antonio Brown   11
Antonio Brown   12
Antonio Brown   13
Antonio Brown   14
Antonio Brown   15
Antonio Brown   16
Antonio Brown   17

CodePudding user response：

You're looking for cumcount.

df['Count'] = df.groupby('Name').cumcount()

Output:

>>> df
               Name  Count
0   Devonta Freeman      1
1   Devonta Freeman      2
2   Devonta Freeman      3
3   Devonta Freeman      4
4   Devonta Freeman      5
5   Devonta Freeman      6
6   Devonta Freeman      7
7   Devonta Freeman      8
8   Devonta Freeman      9
9   Devonta Freeman     10
10  Devonta Freeman     11
11  Devonta Freeman     12
12  Devonta Freeman     13
13  Devonta Freeman     14
14  Devonta Freeman     15
15    Antonio Brown      1
16    Antonio Brown      2
17    Antonio Brown      3
18    Antonio Brown      4
19    Antonio Brown      5
20    Antonio Brown      6
21    Antonio Brown      7
22    Antonio Brown      8
23    Antonio Brown      9
24    Antonio Brown     10
25    Antonio Brown     11
26    Antonio Brown     12
27    Antonio Brown     13
28    Antonio Brown     14
29    Antonio Brown     15
30    Antonio Brown     16
31    Antonio Brown     17