Set index based on same value python dataframe

Question

In python dataframe, I have a data frame like this

index	column A
0	a
1	a
2	b
3	c
4	c
5	c
6	c

I want to create a column that will set index based on the same column's value

index	column A	setIndex
0	a	0
1	a	1
2	b	0
3	c	0
4	c	1
5	c	2
6	c	3

df['setIndex'] = df.groupby('column A').cumcount()

Chris
– Chris

2021-10-07 16:36:10 +00:00
Commented Oct 7, 2021 at 16:36 — Chris
– Chris, Commented Oct 7, 2021 at 16:36
Use groupby.cumcount.

Henry Yik
– Henry Yik

2021-10-07 16:36:42 +00:00
Commented Oct 7, 2021 at 16:36 — Henry Yik
– Henry Yik, Commented Oct 7, 2021 at 16:36

SeaBean · Accepted Answer · 2021-10-07 16:37:55Z

1

You can use .groupby() + .cumcount(), as follows:

df['setIndex'] = df.groupby('column A').cumcount()

Result:

print(df)

  column A  setIndex
0        a         0
1        a         1
2        b         0
3        c         0
4        c         1
5        c         2
6        c         3

answered Oct 7, 2021 at 16:37

SeaBean

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