如何合并多级列结构的数据帧？

import pandas as pd

# 创建多级列结构的数据帧
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
df2 = pd.DataFrame({'C': [7, 8, 9], 'D': [10, 11, 12]})
df1.columns = pd.MultiIndex.from_tuples([('Level1', 'A'), ('Level1', 'B')])
df2.columns = pd.MultiIndex.from_tuples([('Level2', 'C'), ('Level2', 'D')])

# 合并多级列结构的数据帧
merged_df = pd.concat([df1, df2], axis=1)
print(merged_df)

  Level1     Level2    
       A  B       C   D
0      1  4       7  10
1      2  5       8  11
2      3  6       9  12

import pandas as pd

# 创建多级列结构的数据帧
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6], 'key': ['x', 'y', 'z']})
df2 = pd.DataFrame({'C': [7, 8, 9], 'D': [10, 11, 12], 'key': ['x', 'y', 'z']})
df1.columns = pd.MultiIndex.from_tuples([('Level1', 'A'), ('Level1', 'B'), ('Level1', 'key')])
df2.columns = pd.MultiIndex.from_tuples([('Level2', 'C'), ('Level2', 'D'), ('Level2', 'key')])

# 合并多级列结构的数据帧
merged_df = pd.merge(df1.set_index(('Level1', 'key')), df2.set_index(('Level2', 'key')), left_index=True, right_index=True)
print(merged_df)

  Level1       Level2    
       A  B    C   D
key                  
x      1  4    7  10
y      2  5    8  11
z      3  6    9  12