CODEWITHSUNDEEP
pythonpandasdataframe
eztam
eztam

Reputation: 3841

Merge two DataFrames basend on a common index

I want to merge two DataFrames based on their common index. All new index entries from DataFrame B should be added to the result. If both dataframes have an entry for the same index, then the result should only contain the value from DataFrame B.

DataFrame A         DataFrame B
-----------         ------------   
Index  col1         Index   col1
1      1A           1       1B
2      2A           3       3B

Result
------------                   
Index   col1 
1       1B   # Overridden from DataFrame B
2       2A   # From DataSet A
3       3B   # Added from B since it not exists in A

I've tried already the following. But it results in two columns and I want just a single column in my result:

df1 = pd.DataFrame(index= [1, 2],
              data = ['1A', '2A'],
              columns=['col1'])

df2 = pd.DataFrame(index= [1, 3],
               data=['1B', '3B'],
               columns=['col1'])

df3 = pd.merge(df1, df2, how='outer', left_index=True, right_index=True)

Upvotes: 1

Views: 234

Answers (1)

BENY
BENY

Reputation: 323386

By using update + combine_first 

df1.update(df2)
df1
Out[525]: 
      col1
Index     
1       1B
2       2A
df1.combine_first(df2)
Out[526]: 
      col1
Index     
1       1B
2       2A
3       3B

Upvotes: 1

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