CODEWITHSUNDEEP
pythonpandasdataframe
Kallol
Kallol

Reputation: 2189

concat column values with previous row if there is null in another column in same row

I have a data frame like this,

df:

col1      col2       col3
 1        cat          4
nan       dog         nan 
 3        tiger         3
 2        lion          9
 nan      frog         nan
 nan     elephant      nan

I want to create a data frame from this data frame that id there is nan values in col1, col2 values will be added to the previous row value.

for example the desired output data frame will be:

col1     col2             col3
 1      catdog             4
 3       tiger             3
 2     lionfrogelephant    9

How to do this using pandas ?

Upvotes: 1

Views: 401

Answers (1)

jezrael
jezrael

Reputation: 863801

Use forward filling missing values and aggregate join:

cols = ['col1','col3']
df[cols] = df[cols].ffill()
df = df.groupby(cols)['col2'].apply(''.join).reset_index()
print (df)
   col1  col3              col2
0   1.0   4.0            catdog
1   2.0   9.0  lionfrogelephant
2   3.0   3.0             tiger

Or if necessary forward filling missing values in all columns:

df = df.ffill().groupby(['col1','col3'])['col2'].apply(''.join).reset_index()
print (df)
   col1  col3              col2
0   1.0   4.0            catdog
1   2.0   9.0  lionfrogelephant
2   3.0   3.0             tiger

Upvotes: 1

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