Compare dataframes and add new rows in python-CodePudding

I have two pandas dataframes.

df1

col1   col2       col3   col4
A      C0079731   s1     abc
A      C0079731   s2     abc

df2

col1   col2       col3
A      C0079731   s1
A      C0079731   s2
AA     C0079731   s3

I would like to compare col2 and if any 'col3' value is missing, then add to 'df1'. The expected output is:

df1

col1   col2       col3   col4
A      C0079731   s1     abc
A      C0079731   s2     abc
AA     C0079731   s3     abc

I tried so far is merging the two dataframes but how can I get the above expected output.

df_2 = df1.merge(df2, left_on='col2', right_on = 'col2', how = 'inner')

CodePudding user response：

Concat, ffill and then drop duplicates if the table is as simple as you presented it here

pd.concat([df1, df2]).ffill().drop_duplicates()