Python入门5（pandas中merge中的参数how）

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 1 import pandas as pd
 df1 = pd.DataFrame([[1,2,3],[1,10,20],[5,6,7],[3,9,0],[8,0,3]],columns=['x1','x2','x3'])
 df2 = pd.DataFrame([[1,2],[1,10],[1,3],[4,6],[3,9]],columns=['x1','x4'])
 print (df1)
 print (df2)
 df3 = pd.merge(df1,df2,how = 'left',on='x1')
 print (df3)
 df4 = pd.merge(df1,df2,how = 'right',on='x1')
 print (df4)
 df5 = pd.merge(df1,df2,how = 'inner',on='x1')
 print (df5)
 df6 = pd.merge(df1,df2,how = 'outer',on='x1')
 print (df6)