pythonpandasnumpy

How to create a column of increasing value base on other column with same value

all

I have a data frame as below

df = pd.DataFrame.from_dict({'A':[1,1,2], 'B':[10,20,14], "C":[30,40,20]})

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How to create a new column for example newCol which depends on column A. if value at A remains same, then newCol will fill with a increasing integer. if there is a diff value in A, here 2, then the value of newCol will reset and start increasing again.

Thank you.

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Solution

  • Code

    grp = df['A'].ne(df['A'].shift()).cumsum()
df['newCol'] = df['A'].groupby(grp).cumcount().add(1)

    df:

       A   B   C  newCol
0  1  10  30       1
1  1  20  40       2
2  2  14  20       1