索引多级索引数据帧

import pandas as pd

# 创建多级索引
arrays = [
    ['A', 'A', 'B', 'B'],
    ['one', 'two', 'one', 'two']
]
index = pd.MultiIndex.from_arrays(arrays, names=('first', 'second'))

# 创建数据帧
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

df = pd.DataFrame({
    ('A', 'one'): [10],
    ('A', 'two'): [20],
    ('B', 'one'): [30],
    ('B', 'two'): [40]
}, index=[0])

# 设置多级索引
df.columns = pd.MultiIndex.from_tuples(df.columns, names=['letter', 'number'])
print(df)

print(df.loc[(slice(None), 'one'), :])

print(df.xs('A', level='first'))

print(df.loc[('A', 'one'), :])

df.sort_index(inplace=True)

df.swaplevel('first', 'second', axis=0).sort_index()

df.reset_index(inplace=True)

df.droplevel('second')

import pandas as pd

# 创建多级索引数据帧
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)

# 访问数据
print("Accessing specific cell:")
print(df.loc[(slice(None), 'one'), :])

print("\nCross-level access:")
print(df.xs('A', level='first'))

print("\nAccessing with loc:")
print(df.loc[('A', 'one'), :])

# 操作数据
print("\nSorting index:")
df.sort_index(inplace=True)
print(df)

print("\nSwapping levels:")
print(df.swaplevel('first', 'second', axis=0).sort_index())

print("\nResetting index:")
df.reset_index(inplace=True)
print(df)

print("\nDropping a level:")
df.droplevel('second')
print(df)