How to use .add() function to merge two dataframes in python

Question

Please use the image attached as reference .

I have two dataframes

df_class_a

with data :

Subject maximum minimum
Physics  98      50 
Maths    100     45 
Chem     99      65

df_class_b with data

Subject maximum minimum
Maths    100     45 
Physics  98      44 
Chem     85      50 
language 88      54

and I want to merge them to form a new data frame say df_add

Subject maximum minimum
Maths    200     90 
Physics  196     94 
Chem     184     115 
Language  88     54

which will be sum of the dataframes but both of them do not have same rows of data. How can I do it using .add functionality in pandas.

enter image description here

jezrael · Accepted Answer · 2020-10-25 08:45:05Z

1

Another solution:

m = pd.merge(df1, df2, on='Subject', how='outer')
m['maximum'] = m[['maximum_x', 'maximum_y']].sum(axis=1)
m['minimum'] = m[['minimum_x', 'minimum_y']].sum(axis=1)

print(m[['Subject', 'maximum', 'minimum']])

Prints:

    Subject  maximum  minimum
0     Maths    200.0     90.0
1   Physics    196.0     94.0
2      Chem    184.0    115.0
3  language     88.0     54.0

edited Oct 25, 2020 at 8:45

jezrael

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answered Oct 25, 2020 at 8:38

Andrej Kesely

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Comments

jezrael · Accepted Answer · 2020-10-25 08:39:27Z

1

Convert Subject to index in both DataFrames by DataFrame.set_index and then use DataFrame.add with fill_value=0):

df = df_class_a.set_index('Subject').add(df_class_b.set_index('Subject'), fill_value=0)
print (df)
          maximum  minimum
Subject                   
Chem        184.0    115.0
Maths       200.0     90.0
Physics     196.0     94.0
language     88.0     54.0

Or use concat with aggregate sum:

df = pd.concat([df_class_a, df_class_b]).groupby('Subject', as_index=False).sum()
print (df)
    Subject  maximum  minimum
0      Chem      184      115
1     Maths      200       90
2   Physics      196       94
3  language       88       54

edited Oct 25, 2020 at 8:39

answered Oct 25, 2020 at 8:34

jezrael

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Comments

avarice · Accepted Answer · 2020-10-25 08:36:49Z

0

You can try:

df_add = pd.DataFrame({
'Subject': df_class_a['Subject'],
'Maximum': df_class_a['Maximum']+df_class_b['Maximum'],
'Minimum': df_class_a['Minimum']+df_class_b['Minimum']
})

answered Oct 25, 2020 at 8:36

avarice

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1 Comment

jezrael Over a year ago

I chnage data in question for see, why your solution is bad.

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