如何将MultiIndex的第一级作为列？

Question

假设我有一个MultiIndex数据帧,如:

In [1]: arrays = [['one','one','one','two','two','two'],[1,2,3,1,2,3]]      

In [2]: df = pa.DataFrame(randn(6,1),index=pa.MultiIndex.from_tuples(zip(*arrays)),columns=['A'])

In [3]: df                                                                  
Out[3]:                                                                     
              A                                                             
one 1  0.229037                                                             
    2 -1.640695                                                             
    3  0.908127                                                             
two 1 -0.918750                                                             
    2  1.170112                                                             
    3 -2.620850                                                             

我想将其更改为新的数据帧,将列作为MultiIndex数据帧的第一级索引？有一个简单的方法吗？(以下为例)

In [12]: dft = df.ix['one']                                                 

In [13]: dft = dft.rename(columns={'A':'one'})                              

In [14]: dft['two'] = df.ix['two']['A']                                     

In [15]: dft                                                                
Out[15]:                                                                    
        one       two                                                       
1  0.229037 -0.918750                                                       
2 -1.640695  1.170112                                                       
3  0.908127 -2.620850                                                       

Answer 1

也许你正在寻找pandas.unstack:

In [56]: df
Out[56]: 
              A
one 1  0.229037
    2 -1.640695
    3  0.908127
two 1 -0.918750
    2  1.170112
    3 -2.620850

In [57]: df.unstack(level=0)
Out[57]: 
          A          
        one       two
1  0.229037 -0.918750
2 -1.640695  1.170112
3  0.908127 -2.620850