如何在多索引数据框的索引中插入值

import pandas as pd

# 创建多索引数据框
index = pd.MultiIndex.from_product([['A', 'B'], ['x', 'y']], names=['Index1', 'Index2'])
data = [[1, 2], [3, 4], [5, 6], [7, 8]]
df = pd.DataFrame(data, index=index, columns=['Value1', 'Value2'])

# 在已有的索引中插入值
new_index = pd.MultiIndex.from_product([['A', 'B', 'C'], ['x', 'y']], names=['Index1', 'Index2'])
df_reindexed = df.reindex(new_index)

# 在新的索引位置插入值
new_data = [[9, 10], [11, 12]]
df_new = pd.DataFrame(new_data, index=[('C', 'x'), ('C', 'y')], columns=['Value1', 'Value2'])
df_concat = pd.concat([df, df_new])

print(df_reindexed)
print(df_concat)