Merge two dataframes in Python

Question

I have recently started using dataframes in Python and I don't know how can I do the following exercise.

I have two dataframes, both with the same columns (Type column and Count column) like this:

main_df:

Index	Type	Count
0	Album	12
1	Book	4
2	Person	3

df2:

Index	Type	Count
0	Album	9
1	Person	4
2	Film	4

Same Type value can have different Index value, as you can see with Type = Person (Index = 2 in main_df and Index = 1 in df2).

I want to have all data in main_df. In this case result will be:

main_df:

Index	Type	Count
0	Album	21
1	Book	4
2	Person	7
3	Film	4

If Type column value in df2 is already in main_df, simply sum the corresponding Count value of df2. If Type column value in df2 is not in main_df, add that row (Type and Count value) at the end of main_df.

Hope you can help me with this. Thanks in advance.

Nk03 · Accepted Answer · 2021-06-06 13:20:41Z

3

You can try with pd.concat and then use groupby:

main_df = pd.concat([main_df,df2]).groupby('Type', sort=False).agg({'Count': sum}).reset_index()

OUTPUT:

     Type  Count
0   Album     21
1    Book      4
2  Person      7
3    Film      4

answered Jun 6, 2021 at 13:20

Nk03

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Comments

Anurag Dabas · Accepted Answer · 2021-06-06 13:23:36Z

2

try via append(),groupby() and sum():

out=(df1.append(df2)
        .groupby('Type',as_index=False,sort=False)
        .sum())

Output of out:

    Type    Index   Count
0   Album   0       21
1   Book    1       4
2   Person  3       7
3   Film    2       4

answered Jun 6, 2021 at 13:23

Anurag Dabas

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