How to calculate last two week sum for each group ID

** I have Input data frame **

desired Output data frame

I want to calculate the last two week total sum like
twoweekSum= current week total sum + Previous Week total sum i.e. current week is 34 then twoweekSum is 34 week total sum + 33 week total sum.

Please help me in to get in this in like output data frame so I can use that for further analysis.
Thank You folks !

>Solution :

Use:

#convert values to datetimes
df['Date'] = pd.to_datetime(df['Date'])

#convert values to weeks
df['week'] = df['Date'].dt.isocalendar().week

#aggregate sum per ID and weeks, then add missing weeks and sum in rolling
f = lambda x: x.reindex(range(x.index.min(), x.index.max() + 1))
                .rolling(2, min_periods=1).sum()
df1 = df.groupby(['ID', 'week'])['Amount'].sum().reset_index(level=0).groupby('ID').apply(f)

print (df1)
         Amount
ID week        
A  31     320.0
   32     830.0
   33     510.0
   34      40.0

#last add to original DataFrame per ID and weeks
df=df.join(df1.rename(columns={'Amount':'TwoWeekSum'}),on=['ID','week']).drop('week',axis=1)

print (df)
   ID       Date  Amount  TwoWeekSum
0   A 2021-08-03     100       320.0
1   A 2021-08-04     100       320.0
2   A 2021-08-06      20       320.0
3   A 2021-08-07     100       320.0
4   A 2021-08-09     300       830.0
5   A 2021-08-11     100       830.0
6   A 2021-08-12     100       830.0
7   A 2021-08-13      10       830.0
8   A 2021-08-23      10        40.0
9   A 2021-08-24      10        40.0
10  A 2021-08-26      10        40.0
11  A 2021-08-28      10        40.0