Pandas - compute and pivot to get revenue from previous two years-CodePudding

I have a dataframe like as below

df = pd.DataFrame(
    {'stud_id' : [101, 101, 101, 101, 
                  101, 102, 102, 102],
     'sub_code' : ['CSE01', 'CSE01', 'CSE01', 
                   'CSE01', 'CSE02', 'CSE02',
                   'CSE02', 'CSE02'],
     'ques_date' : ['10/11/2022', '06/06/2022','09/04/2022', '27/03/2022', 
                '13/05/2010',  '10/11/2021','11/1/2022', '27/02/2022'],
     'revenue' : [77, 86, 55, 90, 
                65, 90, 80, 67]}
)
df['ques_date'] = pd.to_datetime(df['ques_date'])

I would like to do the below

a) Compute custom financial year based on our organization FY calendar. Meaning, Oct-Dec is Q1, Jan -Mar is Q2,Apr - Jun is Q3 and July to Sep is Q4.

b) Group by stud_id

c) Compute sum of revenue from previous two custom FYs (from a specific date = 20/12/2022). For example, if we are in the FY-2023, I would like to get the sum of revenue for a customer from FY-2022 and FY-2021 separately

So, I tried the below based on this post

I expect my output to be like as below

updated output

CodePudding user response：

It seems you just need to first fine the quarter year, filter to only include 2021 and 2022 rows, and then summarize & pivot:

(df.assign(
    qyear = pd.to_datetime(df['ques_date'], dayfirst=True).dt.to_period('Q-SEP').dt.qyear
  )[lambda x: x.qyear.isin([2021, 2022])]
  .assign(qyear=lambda x: x.qyear.astype('category').cat.set_categories([2021, 2022]))
  .groupby(['stud_id', 'qyear'])
  .revenue.sum()
  .unstack(level=1)
  .add_prefix('rev_')
  .reset_index(drop=False))

#qyear  stud_id  rev_2021  rev_2022
#0          101         0       231
#1          102         0       157

For the update:

df['qyear'] = pd.to_datetime(df['ques_date'], dayfirst=True).dt.to_period('Q-SEP').dt.qyear.astype('category').cat.set_categories([2021, 2022])
df.groupby(['stud_id', 'sub_code', 'qyear']).revenue.sum().unstack(level=1, fill_value=0).add_prefix('rev_').reset_index(drop=False)

sub_code  stud_id qyear  rev_CSE01  rev_CSE02
0             101  2021          0          0
1             101  2022        231          0
2             102  2021          0          0
3             102  2022          0        157