如何在Pandas上使用group by应用累积自定义聚合函数

import pandas as pd

data = {'Category': ['A', 'A', 'B', 'B', 'A', 'B'],
        'Value': [10, 15, 12, 17, 13, 9]}
df = pd.DataFrame(data)

def cumulative_sum(x):
    return x.cumsum()

df['Cumulative Sum'] = df.groupby('Category')['Value'].transform(cumulative_sum)

print(df)

import pandas as pd

data = {'Category': ['A', 'A', 'B', 'B', 'A', 'B'],
        'Value': [10, 15, 12, 17, 13, 9]}
df = pd.DataFrame(data)

def cumulative_sum(x):
    return x.cumsum()

df['Cumulative Sum'] = df.groupby('Category')['Value'].transform(cumulative_sum)

print(df)