Pandas: How to concatenate dataframes with different columns?

Question

I tried to find the answer in the official Pandas documentation, but found it more confusing than helpful. Basically I have two dataframes with overlapping, but not identical column lists:

df1:
   A   B
0  22  34
1  78  42

df2:
   B   C
0  76  29
1  11  67

I want to merge/concatenate/append them so that the result is

df3:
   A   B   C
0  22  34  nan
1  78  42  nan
2  nan 76  29
3  nan 11  67

Should be fairly simple, but I've tried several intuitive approaches and always got errors. Can anybody help me?

Answer 1

If you just want to concatenate the dataframes you can use.

pd.concat([df1,df2])

output:

      A   B     C
0  22.0  34   NaN
1  78.0  42   NaN
0   NaN  76  11.0
1   NaN  11  67.0

Then you can reset_index to recreate a simple incrementing index.

pd.concat([df,df2]).reset_index(drop = True)

Output:

      A   B     C
0  22.0  34   NaN
1  78.0  42   NaN
2   NaN  76  11.0
3   NaN  11  67.0