How can I enumerate a sublevel in a multiindex in pandas simply?

Question

I would like to create a new column with the enumeration of Objects column based on membership in Name

Name	Objects
A	phone
B	phone
B	keys
B	chewing gum
C	radio
C	chewing gum

into

Name	Object no.	Objects
A	1	phone
B	1	phone
B	2	keys
B	3	chewing gum
C	1	radio
C	2	chewing gum

I suppose that there should be a really easy way to do it

The rows don't match between input and output. – Ynjxsjmh May 04 '22 at 13:52 — Ynjxsjmh, May 04 '22 at 13:52

score 2 · Accepted Answer · answered May 04 '22 at 13:56

You can try groupy then cumcount

df['Object no.'] = df.groupby('Name').cumcount().add(1)

print(df)

  Name      Objects  Object no.
0    A        phone           1
1    B        phone           1
2    B         keys           2
3    B  chewing gum           3
4    C        radio           1
5    C  chewing gum           2

How can I enumerate a sublevel in a multiindex in pandas simply?

1 Answers1