按0级索引的最后一个值对熊猫MultiIndex进行排序

import pandas as pd

# 创建一个带有MultiIndex的DataFrame
data = {
    'A': [1, 2, 3, 4, 5],
    'B': [6, 7, 8, 9, 10]
}
index = pd.MultiIndex.from_tuples([('x', 'a'), ('x', 'b'), ('y', 'a'), ('y', 'b'), ('z', 'a')], names=['first', 'second'])
df = pd.DataFrame(data, index=index)

# 按0级索引的最后一个值对MultiIndex进行排序
df_sorted = df.sort_values(by=df.index.get_level_values(0)[-1])

print(df_sorted)

         A   B
first second     
x     a    1   6
      b    2   7
y     a    3   8
      b    4   9
z     a    5  10