按索引合并两个数据框

按索引合并两个数据框

使用

merge

，默认情况下是内部联接：

pd.merge(df1, df2, left_index=True, right_index=True)

或

join

，默认情况下为左连接：

df1.join(df2)

或

concat

，默认情况下为外部联接：

pd.concat([df1, df2], axis=1)

样品 ：

df1 = pd.Dataframe({'a':range(6),         'b':[5,3,6,9,2,4]}, index=list('abcdef'))print (df1)   a  ba  0  5b  1  3c  2  6d  3  9e  4  2f  5  4df2 = pd.Dataframe({'c':range(4),         'd':[10,20,30, 40]}, index=list('abhi'))print (df2)   c   da  0  10b  1  20h  2  30i  3  40

---

#default inner joindf3 = pd.merge(df1, df2, left_index=True, right_index=True)print (df3)   a  b  c   da  0  5  0  10b  1  3  1  20#default left joindf4 = df1.join(df2)print (df4)   a  b    c     da  0  5  0.0  10.0b  1  3  1.0  20.0c  2  6  NaN   NaNd  3  9  NaN   NaNe  4  2  NaN   NaNf  5  4  NaN   NaN#default outer joindf5 = pd.concat([df1, df2], axis=1)print (df5)     a    b    c     da  0.0  5.0  0.0  10.0b  1.0  3.0  1.0  20.0c  2.0  6.0  NaN   NaNd  3.0  9.0  NaN   NaNe  4.0  2.0  NaN   NaNf  5.0  4.0  NaN   NaNh  NaN  NaN  2.0  30.0i  NaN  NaN  3.0  40.0