Python: Find the first occurance of 1 in a column within a group and repeat the values for subsequen-CodePudding

I have a dataframe with repeating ID as below

ID	of_flag	os_flag
1	0	1
1	1	0
2	1	0
2	0	1
2	0	0

I need to create updated column 'of_flag_up' and 'os_flag_up' based on the of_flag and os_flag columns respectively which looks for the first occurance of 1 within each ID group and fill 1 for the rest of the rows as below

ID	of_flag	os_flag	of_flag_up	os_flag_up
1	0	1	0	1
1	1	0	1	1
2	1	0	1	0
2	0	1	1	1
2	0	0	1	1

Any help on this would be appreciated. Thanks

CodePudding user response：

You can groupby "ID" and find the cumulative max for each group using cummax and assign them to new columns:

df[['of_flag_up','os_flag_up']] = df.groupby('ID')[['of_flag', 'os_flag']].cummax()

Output:

   ID  of_flag  os_flag  of_flag_up  os_flag_up
0   1        0        1           0           1
1   1        1        0           1           1
2   2        1        0           1           0
3   2        0        1           1           1
4   2        0        0           1           1