Pandas Merge and Complete rows with same id

Question

Here is an extract of my dataframe :

ID	LU	MA	ME	JE	VE	SA	DI
200	B		B	B
201	C	C	C	C	C
211	A
211		D	D	D
211					B
213						A	A
216	K	K	K	K
216					K
217	B	B	B	B	B

I have some rows with same ID and want to "merge" them into only one row while completing them. Here is an example of what I want to have as a result :

ID	LU	MA	ME	JE	VE	SA	DI
200	B		B	B
201	C	C	C	C	C
211	A	D	D	D	B
213						A	A
216	K	K	K	K	K
217	B	B	B	B	B

I'm new to pandas dataframes and have try to use drop_duplicates method but I need something different because of the restriction on keep parameters. Also the dataframe is sorted by ID.

Answer 1

If there is only one non empty value per groups use:

df = df.replace('',np.nan).groupby('ID', as_index=False).first().fillna('')

If possible multiple values and need unique values in original order use lambda function:

print (df)
    ID LU MA ME JE VE SA DI
0  201  B     C  B         
1  201  C  C  C  B  C    


f = lambda x: ','.join(dict.fromkeys(x.dropna()).keys())
df = df.replace('',np.nan).groupby('ID', as_index=False).agg(f)
print (df)
    ID   LU MA ME JE VE SA DI
0  201  B,C  C  C  B  C