How do I fill information of a blank row from another row where information is available in Python?

Mufeez 0
Viewed 20

Let's say I have a data frame

A B C
A1 R3 P5
A2 R2 P4
A2 NaN P4
A1 NaN NaN

I want to fill in information for the 3rd and 4th rows from the 2nd and 1st rows since column A values match those two rows. The expected data frame is as follows:

A B C
A1 R3 P5
A2 R2 P4
A2 R2 P4
A1 R3 P5

Can you please help me with it?

pandas numpy python
2 Answers

Assuming a single non-NA value per A

You can use a self merge:

out = df[['A']].merge(df.dropna(), how='left')

Or, if there is a chance of duplicated rows:

out = df[['A']].merge(df.dropna().drop_duplicates(), how='left')

output:

    A   B   C
0  A1  R3  P5
1  A2  R2  P4
2  A2  R2  P4
3  A1  R3  P5
mozway0

here is one way to do it.

sorting by column 'A', forward filling the null values and then re-sorting by index

df.sort_values(['A'] ).ffill().sort_index()


     A   B   C
0   A1  R3  P5
1   A2  R2  P4
2   A2  R2  P4
3   A1  R3  P5
userCaFe0
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