dataframe重新设置index

frame
a b c d
0 0 7 one 0
1 1 6 one 1
2 2 5 one 2
3 3 4 two 0
4 4 3 two 1
5 5 2 two 2
6 6 1 two 3

frame2=frame.set_index([‘c’,‘d’])
#set_index函数会生成一个新的dataframe，新的dataframe实用一个或多个列作为索引，默认情况下这些列从dataframe中移除

frame2
a b
c d
one 0 0 7
1 1 6
2 2 5
two 0 3 4
1 4 3
2 5 2
3 6 1

frame.set_index([‘c’,‘d’],drop=False) #可以用drop=False不移除
a b c d
c d
one 0 0 7 one 0
1 1 6 one 1
2 2 5 one 2
two 0 3 4 two 0
1 4 3 two 1
2 5 2 two 2
3 6 1 two 3

frame2.reset_index() #reset_index() 是set_index() 的反向操作
c d a b
0 one 0 0 7
1 one 1 1 6
2 one 2 2 5
3 two 0 3 4
4 two 1 4 3
5 two 2 5 2
6 two 3 6 1