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I have two dataframes df1, df2. 

df1=pd.DataFrame(columns=['name','yr'])
df1.name=['a','b','c','b','d','a']
df1.yr=[2017,2016,2017,2018,2018,2019]
df2=pd.DataFrame(index=[2016,2017,2018,2019],columns=['a','b','c','d'],data= np.random.randn(4,4))

What I want is add new column 'z' with values from df2, corresponding 'name' and 'year'.

iteration using for statement is not my consideration.

*added) 'merge' cannot be used because matching data in df1 is in index&column of df2

Malik Asad
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장현아
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1 Answers1

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Use DataFrame.lookup:

df1['z'] = df2.lookup(df1['yr'], df1['name'])
print (df1)

  name    yr         z
0    a  2017 -0.578600
1    b  2016  0.997345
2    c  2017 -2.426679
3    b  2018 -0.866740
4    d  2018 -0.094709
5    a  2019  1.491390
jezrael
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