CODEWITHSUNDEEP
pythonpandas
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Reputation: 155

Python/Pandas - Add counter to DataFrame based on column values

Using Python, I have a panda dataframe

A B 
1 red
2 blue
3 green
4 red
5 green
6 orange
7 red

I would like to create a column with an incremental counter based on the values in B. That is to resolve to

A B      C
1 red    1
2 blue   1
3 green  1
4 red    2
5 green  2
6 orange 1
7 red    3

Upvotes: 2

Views: 1242

Answers (1)

Ted Petrou
Ted Petrou

Reputation: 62037

Groupby each color and then use the cumcount method.

df['C'] = df.groupby('B').cumcount() + 1

   A       B  C
0  1     red  1
1  2    blue  1
2  3   green  1
3  4     red  2
4  5   green  2
5  6  orange  1
6  7     red  3

Upvotes: 4

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