Merge or concat two df by index

Question

I have the following issue: I want to concat or merge two dataframes with different length and partly different indexes:

data1:

index	data1
1	16
2	37
3	18
7	49

data2:

index	data2
2	74
3	86
4	12
6	97
12	35

They should be merged in the way, that the output looks like:

index	data1	data2
1	16	NaN
2	37	74
3	18	86
4	NaN	12
6	NaN	97
7	49	NaN
12	NaN	35

I hope you can help me out.

Thanks in advance

Answer 1

You can use join:

out = df1.join(df2, how='outer')
print(out)

# Output
       data1  data2
index              
1       16.0    NaN
2       37.0   74.0
3       18.0   86.0
4        NaN   12.0
6        NaN   97.0
7       49.0    NaN
12       NaN   35.0

Or you can use merge:

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

Or you can use concat:

out = pd.concat([df1, df2], axis=1).sort_index()