如何在Pandas中展平groupby操作的结果？

import pandas as pd

# 假设df是一个DataFrame
df = pd.DataFrame({
    'A': ['foo', 'bar', 'foo', 'bar', 'foo', 'bar', 'foo', 'foo'],
    'B': ['one', 'one', 'two', 'three', 'two', 'two', 'one', 'three'],
    'C': [1, 2, 3, 4, 5, 6, 7, 8],
    'D': [10, 20, 30, 40, 50, 60, 70, 80]
})

# 进行groupby操作
grouped = df.groupby(['A', 'B']).sum()

# 展平结果
flattened = grouped.reset_index()
print(flattened)

import pandas as pd

# 假设df是一个DataFrame
df = pd.DataFrame({
    'A': ['foo', 'bar', 'foo', 'bar', 'foo', 'bar', 'foo', 'foo'],
    'B': ['one', 'one', 'two', 'three', 'two', 'two', 'one', 'three'],
    'C': [1, 2, 3, 4, 5, 6, 7, 8],
    'D': [10, 20, 30, 40, 50, 60, 70, 80]
})

# 进行groupby操作并聚合
grouped = df.groupby(['A', 'B']).agg({'C': 'sum', 'D': 'mean'})

# 展平多级索引
flattened = grouped.unstack().reset_index()
print(flattened)

import pandas as pd

# 假设df是一个DataFrame
df = pd.DataFrame({
    'A': ['foo', 'bar', 'foo', 'bar', 'foo', 'bar', 'foo', 'foo'],
    'B': ['one', 'one', 'two', 'three', 'two', 'two', 'one', 'three'],
    'C': [1, 2, 3, 4, 5, 6, 7, 8],
    'D': [10, 20, 30, 40, 50, 60, 70, 80]
})

# 进行groupby操作并聚合
grouped = df.groupby(['A', 'B']).agg({'C': 'sum', 'D': 'mean'})

# 转换为长格式
melted = grouped.reset_index().melt(id_vars=['A', 'B'], var_name='Metric', value_name='Value')

# 转换回宽格式
flattened = melted.pivot(index=['A', 'B'], columns='Metric', values='Value').reset_index()
print(flattened)