简化pandas groupby().agg()的代码

import pandas as pd

# 创建一个示例数据集
data = {'A': ['foo', 'bar', 'foo', 'bar', 'foo', 'bar', 'foo', 'foo'],
        'B': ['one', 'one', 'two', 'two', 'two', 'one', 'two', 'one'],
        'C': [1, 2, 3, 4, 5, 6, 7, 8],
        'D': [10, 20, 30, 40, 50, 60, 70, 80]}
df = pd.DataFrame(data)

# 使用transform函数简化groupby().agg()的代码
df['sum_C'] = df.groupby(['A', 'B'])['C'].transform('sum')
df['mean_D'] = df.groupby(['A', 'B'])['D'].transform('mean')

print(df)

     A    B  C   D  sum_C  mean_D
0  foo  one  1  10      9      30
1  bar  one  2  20      2      20
2  foo  two  3  30      8      50
3  bar  two  4  40      4      40
4  foo  two  5  50      8      50
5  bar  one  6  60      2      20
6  foo  two  7  70      8      50
7  foo  one  8  80      9      30