Concat python dataframes based on unique rows

user_2079875 0
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My dataframe reads like :

df1

user_id    username firstname lastname 
 123         abc      abc       abc
 456         def      def       def 
 789         ghi      ghi       ghi

df2

user_id     username  firstname lastname
 111         xyz       xyz       xyz
 456         def       def       def
 234         mnp       mnp        mnp

Now I want a output dataframe like 

 user_id    username firstname lastname 
 123         abc      abc       abc
 456         def      def       def 
 789         ghi      ghi       ghi
 111         xyz       xyz       xyz
 234         mnp       mnp        mnp

As user_id 456 is common across both the dataframes. I have tried groupby on user_id groupby(['user_id']) . But looks like groupby need to be followed by some aggregation which I don't want here.

pandas-groupby pandas python
4 Answers

One can also use append + drop_duplicates.

df1.append(df2)
df1.drop_duplicates(inplace=True)
user_70412440
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