用多级索引构建新的pandas Dataframe

import pandas as pd

# 创建一个示例数据
data = {
    ('A', 'foo'): [1, 2, 3],
    ('A', 'bar'): [4, 5, 6],
    ('B', 'foo'): [7, 8, 9],
    ('B', 'bar'): [10, 11, 12]
}

# 使用多级索引创建 DataFrame
index = pd.MultiIndex.from_tuples([('group1', 'subgroup1'), ('group1', 'subgroup2'), ('group2', 'subgroup1')], names=['group', 'subgroup'])
df = pd.DataFrame(data, index=index)

print(df)

              foo  bar
group  subgroup        
group1 subgroup1   1    4
       subgroup2   2    5
group2 subgroup1   7   10

import pandas as pd

# 使用 from_tuples 方法创建多级索引
index = pd.MultiIndex.from_tuples([('group1', 'subgroup1'), ('group1', 'subgroup2'), ('group2', 'subgroup1')], names=['group', 'subgroup'])

# 访问特定层级的数据
df.loc[('group1', 'subgroup1'), 'foo']

# 使用切片访问数据
df.loc[('group1', slice(None)), 'foo']

# 重置多级索引为默认的整数索引
df_reset = df.reset_index()