Filling empty cells in python (import dataset from excel)

Question

I have a dataset where I want to fill the columns and rows in python as shown below:

Dataset:

| P | Q |    
|678|1420|
|678|---|
|609|---|
|583|1260|
|---|1260|
|---|1261|
|---|1262|
|584|1263|
|---|403|
|---|---|

Expected Result:

| P | Q |
|678|1420|
|678|1420|
|609|---|
|583|1260|
|583|1260|
|583|1261|
|583|1262|
|584|1263|
|584|403|
|584|403|

I have filled the column P using fillna() but cannot do the same for column Q since the values needs to be filled for key pair.

can someone please help.

Answer 1

With your shown samples, please try following.

df['P'] = df['P'].ffill()
df['Q'] = df.groupby('P')['Q'].ffill()

Output will be as follows:

    P        Q
0   678.0   1420.0
1   678.0   1420.0
2   609.0   
3   583.0   1260.0
4   583.0   1260.0
5   583.0   1261.0
6   583.0   1262.0
7   584.0   1263.0
8   584.0   403.0
9   584.0   403.0

ffill documentation