基于现有列的pandas多索引数据帧中的新列

import pandas as pd

# 创建一个多索引数据帧
arrays = [
    ['A', 'A', 'B', 'B'],
    ['one', 'two', 'one', 'two']
]
index = pd.MultiIndex.from_arrays(arrays, names=('first', 'second'))
df = pd.DataFrame({'value': [10, 20, 30, 40]}, index=index)
print(df)

              value
first second       
A     one        10
       two        20
B     one        30
       two        40

# 基于现有列创建新列
df['new_value'] = df['value'] * 2
print(df)

              value  new_value
first second                  
A     one        10         20
       two        20         40
B     one        30         60
       two        40         80

# 假设我们有一个新的索引
new_index = pd.MultiIndex.from_arrays([['A', 'B'], ['one', 'two']], names=('first', 'second'))

# 重新设置索引
df = df.reset_index().set_index(new_index)
print(df)

              value  new_value
first second                  
A     one        10         20
B     two        40         80