How to divide two dataframes with different length and duplicated indexs in Python

Question

Here is my code and I want to get the expected output, but, division of dataframes does not work, what is wrong here?

import pandas as pd
data1 = {'name':['A', 'C', 'D'], 'cond_a':['B','B','B'], 'value':[10,12,14]}
data2 = {'name':['A', 'C', 'D','D','A'], 'cond_a':['G','G','G','G','G'], 'value':[5,6,7,3,2]}

df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

df1.set_index('name', inplace=True)
df2.set_index('name', inplace=True)


df2['new_col'] = df2['value'] / df1['value']

expected output:

     cond_a  value    new_col
name        
   A    G     5        5/10
   C    G     6        6/12
   D    G     7        7/14
   D    G     3        3/14        
   A    G     2        2/10

Answer 1

As long as df1 has a unique index, you can reindex it on df2 when performing the division:

df2['new_col'] = df2['value'] / df1['value'].reindex(df2.index)

The resulting output:

     cond_a  value   new_col
name                        
A         G      5  0.500000
C         G      6  0.500000
D         G      7  0.500000
D         G      3  0.214286
A         G      2  0.200000