pandas进行数据的交集与并集方式的数据合并方法

In [26]: df1
Out[26]: 
 data1 key
0  0 b
1  1 b
2  2 a
3  3 c
4  4 a
5  5 a
6  6 b

In [27]: df2
Out[27]: 
 data2 key
0  0 a
1  1 b
2  2 d
3  3 b

In [28]: pd.merge(df1,df2)
Out[28]: 
 data1 key data2
0  0 b  1
1  0 b  3
2  1 b  1
3  1 b  3
4  6 b  1
5  6 b  3
6  2 a  0
7  4 a  0
8  5 a  0

In [29]: pd.merge(df1,df2,how='inner')
Out[29]: 
 data1 key data2
0  0 b  1
1  0 b  3
2  1 b  1
3  1 b  3
4  6 b  1
5  6 b  3
6  2 a  0
7  4 a  0
8  5 a  0

In [30]: result_inner = pd.merge(df1,df2,how='inner')
In [31]: result_default = pd.merge(df1,df2)

In [32]: result_inner == result_default
Out[32]: 
 data1 key data2
0 True True True
1 True True True
2 True True True
3 True True True
4 True True True
5 True True True
6 True True True
7 True True True
8 True True True

In [35]: result_outer = pd.merge(df1,df2,how='outer')

In [36]: result_outer
Out[36]: 
 data1 key data2
0  0.0 b 1.0
1  0.0 b 3.0
2  1.0 b 1.0
3  1.0 b 3.0
4  6.0 b 1.0
5  6.0 b 3.0
6  2.0 a 0.0
7  4.0 a 0.0
8  5.0 a 0.0
9  3.0 c NaN
10 NaN d 2.0