How to apply a function to groupby method in pandas?-CodePudding

I have a data frame like this.

Company	Type	Balance
First	D	15
First	D	30
First	C	40
Second	D	10
Second	C	12
Second	C	15

I want to create a function that adds balance if the type is C and subtract balance if the type is D. How can I do it in the pandas groupby method using apply function?

My output should be like this:

Company	Type	Balance	New Balance
First	D	15	-15
First	D	30	-45
First	C	40	-5
Second	D	10	-10
Second	C	12	2
Second	C	15	17

CodePudding user response：

Use where:

df['New Balance'] = df['Balance'].where(df['Type'] != 'D', df['Balance']*-1) \
                                 .groupby(df['Company']).cumsum()
print(df)

# Output
  Company Type  Balance  New Balance
0   First    D       15          -15
1   First    D       30          -45
2   First    C       40           -5
3  Second    D       10          -10
4  Second    C       12            2
5  Second    C       15           17

CodePudding user response：

Use:

temp = df['type']=='c'
df['new'] = temp.replace(False, -1).replace(True, 1)*df['bal']
df.groupby('company')['new'].cumsum()

output: