MultiIndex对象

import pandas as pd

import numpy as np

from pandas import DataFrame

创建方式一：元组列表

m_index1=pd.Index([("A","x1"),("A","x2"),("B","y1"),("B","y2"),("B","y3")],name=["class1","class2"])

df1=DataFrame(np.random.randint(1,10,(5,3)),index=m_index1)

df1

结果如下：

创建方式二：特定结构

例如**from_arrays()

class1=["A","A","B","B"]

class2=["x1","x2","y1","y2"]

m_index2=pd.MultiIndex.from_arrays([class1,class2],names=["class1","class2"])

df2=DataFrame(np.random.randint(1,10,(4,3)),index=m_index2)

df2

结果如下：

创建方式三：笛卡尔积

from_product()从多个集合的笛卡尔积创建MultiIndex对象。

m_index3=pd.MultiIndex.from_product([["A","B"],['x1','y1']],names=["class1","class2"])

df3=DataFrame(np.random.randint(1,10,(2,4)),columns=m_index3)

df3

MultiIndex(levels=[['A', 'B'], ['x1', 'y1']],

          labels=[[0, 0, 1, 1], [0, 1, 0, 1]],

          names=['class1', 'class2'])

结果如下：