Pandas多层索引降级：直接去除与合并列名的两种实用方法

import pandas as pd
import numpy as np
df = pd.DataFrame(np.arange(0, 14).reshape(7,2),columns =['a','b'] )
df.a = df.a %3
df['who'] = 'Bob'
df.loc[df.a%4==0,'who'] = 'Alice'

gp1 = df.groupby('who').agg({'b':[sum,np.max, np.min], 'a':sum})
gp1

#有层次的索引访问方法
gp1.loc['Bob', ('b', 'sum')]

28.0

gp2 = gp1.copy(deep=True)
gp2.columns = gp1.columns.droplevel(0)
gp2

gp3 = gp1.copy(deep=True)
gp3.columns = ["_".join(x) for x in gp3.columns.ravel()]
gp3