我有以下PandasDataFrame：

df = pd.DataFrame({"A": ["foo", "foo", "foo", "foo", "foo",
                         "bar", "bar", "bar", "bar",'foo' ],
                   "B": ["one", "one", "one", "two", "two",
                         "one", "one", "two", "two", 'two'],
                   "C": ["small", "large", "large", "small",
                         "small", "large", "small", "small",
                         "large", 'large'],
                   "D": [1, 2, 2, 3, 3, 4, 5, 6, 7,8],
               })

输出如下：

print(df)

    A   B   C       D
0   foo one small   1
1   foo one large   2
2   foo one large   2
3   foo two small   3
4   foo two small   3
5   bar one large   4
6   bar one small   5
7   bar two small   6
8   bar two large   7
9   foo two large   8

那么我将按如下方式创建透视表：

table = pd.pivot_table(df, values='D', index=['A'],
                    columns=['B','C'])

输出如下：

print(table)

B   one             two
C   large   small   large   small
A               
bar   4      5       7        6
foo   2      1       8        3

如何将large和small之间的差值（large-small）相加以得到one和two（下表中的diff）？

B   one                 two
C   large   small diff  large   small difff
A               
bar   4        5   -1     7       6    1
foo   2        1    1     8       3    5

我看到了一些以前的答案，但只处理了1列。此外，理想情况下，将使用aggfunc完成
此外，如何将表格重新转换为初始格式？预期输出为：

A   B   C     D 
0  foo one small 1 
1  foo one large 2 
2  foo one large 2 
3  foo two small 3 
4  foo two small 3 
5  bar one large 4 
6  bar one small 5 
7  bar two small 6 
8  bar two large 7 
9  foo two large 8 
10 bar one diff -1 
11 bar two diff 1 
12 foo one diff 1 
13 foo two diff 5

提前感谢您的帮助！