Groupby first by a conditional value

I have a pandas dataframe, like this:

I would like to group per ID and the first date on status is equal 1.

Expected output:

afteer this I will merge this new DF with previous DF. Final DF:

I tried many ways to do this, but unsuccessful

>Solution :

You can filter the status 1 rows, and get the first (or min depending on the use case) per group, then merge to the orginal dataframe:

df2 = (df[df['status'].eq(1)]
       .groupby('ID', as_index=False)
       ['date'].first() # could also use "min()"
       .rename(columns={'date': 'first_status'})
      )

df.merge(df2, on='ID')

output:

   ID        date  status first_status
0  10  2022-01-01       0   2022-01-03
1  10  2022-01-02       0   2022-01-03
2  10  2022-01-03       1   2022-01-03
3  10  2022-01-04       1   2022-01-03
4  10  2022-01-05       1   2022-01-03
5  23  2022-02-02       0   2022-02-04
6  23  2022-02-03       0   2022-02-04
7  23  2022-02-04       1   2022-02-04
8  23  2022-02-05       1   2022-02-04
9  23  2022-02-06       1   2022-02-04

intermediate df2:

   ID first_status
0  10   2022-01-03
1  23   2022-02-04