如何使用MultiIndex在数据框中选择一个值？

import pandas as pd

# 创建一个示例 DataFrame
arrays = [
    ['2020', '2020', '2021', '2021'],
    ['Jan', 'Feb', 'Jan', 'Feb']
]
index = pd.MultiIndex.from_arrays(arrays, names=('Year', 'Month'))
data = {'Value': [10, 20, 30, 40]}
df = pd.DataFrame(data, index=index)

print(df)

              Value
Year Month       
2020 Jan         10
      Feb         20
2021 Jan         30
      Feb         40

# 选择 2020 年 1 月的数据
selected_data = df.loc[('2020', 'Jan')]
print(selected_data)

Value    10
Name: (2020, Jan), dtype: int64

# 去除重复索引
df = df[~df.index.duplicated(keep='first')]

# 检查和调整索引层次
arrays = [
    ['2020', '2020', '2021', '2021'],
    ['Jan', 'Feb', 'Jan', 'Feb']
]
index = pd.MultiIndex.from_arrays(arrays, names=('Year', 'Month'))
df.index = index