data = pd.DataFrame(np.arange(1,10).reshape(3,3),index=["a","b","c"],columns=["A","B","C"])
  print(data)
  '''
    A B C
  a 1 2 3
  b 4 5 6
  c 7 8 9
  '''
  #将列索引为B的列变成data的行索引
  print(data.set_index("B"))
  '''
   A C
  B
  2 1 3
  5 4 6
  8 7 9
  '''
  #获取行索引
  print(data.set_index("B").index)
  #Int64Index([2, 5, 8], dtype='int64', name='B')
  #获取列索引
  print(data.set_index("B").columns)
  #Index(['A', 'C'], dtype='object')
  #将列索引为A和C的列变成行索引，层次化索引
  print(data.set_index(["A","C"]))
  '''
     B
  A C
  1 3 2
  4 6 5
  7 9 8
  '''

  data = pd.DataFrame(np.arange(1,10).reshape(3,3),index=["a","b","c"],columns=["A","B","C"])
  print(data)
  '''
    A B C
  a 1 2 3
  b 4 5 6
  c 7 8 9
  '''
  print(data.set_index(["C"]))
  '''
    A B
  C
  3 1 2
  6 4 5
  9 7 8
  '''
  #相对于data来说行索引从原来的a、b、c变成了0、1、2
  #在使用set_index方法的时候行索引就已经被修改了
  print(data.set_index(["C"]).reset_index())
  '''
    C A B
  0 3 1 2
  1 6 4 5
  2 9 7 8
  '''
  print(data.index)
  #Index(['a', 'b', 'c'], dtype='object')
  print(data.set_index(["C"]).reset_index().index)
  #RangeIndex(start=0, stop=3, step=1)
  print(data.set_index(["C"]).reset_index().columns)
  #Index(['C', 'A', 'B'], dtype='object')