如何使用平均分组列添加行

我有一个像下面这样的数据框。 每个水果加一行，其中 我知道如何生成一个新列来显示每个水果的平均价格，但我不知道如何用这个平均值添加一行。 你能帮我吗?

import numpy as np
import pandas as pd
fruit = ['apple','apple','banana','banana','kiwi','kiwi','grape','grape']
ftype = ['one','two','one','two','three','one','one','two']
resource = ['us','us','us','us','us','us','us','us']
price = [100,150,200,300,120,300,400,500]
df = pd.DataFrame({'fruit':fruit,'ftype':ftype,'resource':resource,'price':price})
print(df)

原始dataframe:

    fruit  ftype  price resource
0   apple    one    100       us
1   apple    two    150       us
2  banana    one    200       us
3  banana    two    300       us
4    kiwi  three    120       us
5    kiwi    one    300       us
6   grape    one    400       us
7   grape    two    500       us

我想产生:

    fruit  ftype  price resource
0   apple    one    100       us
1   apple    two    150       us
    apple    avg    125      all
2  banana    one    200       us
3  banana    two    300       us
   banana    avg    250       all
4    kiwi  three    120       us
5    kiwi    one    300       us
     kiwi    avg    210       all
6   grape    one    400       us
7   grape    two    500       us
    grape    avg    450       all

问题来源StackOverflow 地址：/questions/59386739/pandas-how-to-add-rows-with-average-grouped-columns