How To Perform Forward Fill Logic In Pandas Based On 'ent_id' If It Does Not Exist For Successive Date Then Perform Forward Fill?

let's say i have a data frame as effective_date,ent_id,val 2020-02-03,101,aa 2020-02-03,102,ab 2020-02-03,103,ac 2020-02-03,105,ad 2020-02-04,107,ba 2020-02-04,103,bd 2020-02-04,1

Solution 1:

you can just pivot, ffill, then unstack:

(df.pivot(index='effective_date', columns='ent_id')
   .ffill().stack().reset_index()
)

Output:

effective_dateent_idval02020-02-03     101aa12020-02-03     102ab22020-02-03     103ac32020-02-03     105ad42020-02-04     101aa52020-02-04     102bn62020-02-04     103bd72020-02-04     105bv82020-02-04     106bs92020-02-04     107ba102020-02-04     109be112020-02-05     101aa122020-02-05     102cn132020-02-05     103bd142020-02-05     105bv152020-02-05     106cs162020-02-05     107ba172020-02-05     109ce182020-02-05     113cd192020-02-05     115cv202020-02-05     117ca