如何將小計列添加到多級列 dataframe？

Question

我有一個 dataframe，有 3 個級別的多索引列：

quarter           Q1                        Q2                        Totals
year              2021        2022           2021         2022                      
                 qty orders  qty orders    qty orders   qty orders   qty orders
month name                                       
January          40  2        5   1         1   2         0 0             46  5
February         20  8        2   3         4   6         0 0             26  17
March            2  10        7   4         3   3         0 0             12  17
Totals           62 20       14   8         8   11        0 0             84  39

按級別 (0,2) 進行分組后，我得到以下小計 dataframe：

quarter           Q1           Q2          Totals                     
                 qty orders  qty orders    qty orders  
month name                                       
January          45  3        1   2         46   5     
February         22  10       4   6         26   16     
March            9  14        3   3         12   17   
Totals           76 28        8   11        84   39

我需要將第二個插入第一個，而不打亂列、級別或索引，以便我得到以下 dataframe：

quarter       Q1                                   Q2                        Totals
year        2021        2022      Subtotal    2021        2022     Subtotal                 
            qty orders qty orders qty orders qty orders qty orders qty orders qty orders
month name                                       
January     40  2       5   1     45   3       1  2       0  0       1  2     46  5
February    20  8       2   3     22   10      4  6       0  0       4  6     26  16
March       2  10       7   4     9    14      3  3       0  0       3  3     12  17
Totals      62 20      14   8     76   28      8  11      0  0       8  11    84 39

我該怎么做呢？

Answer 1

使用您最初的 dataframe（在 groupby 之前）：

import pandas as pd


df = pd.DataFrame(
    [
        [40, 2, 5, 1, 1, 2, 0, 0],
        [20, 8, 2, 3, 4, 6, 0, 0],
        [2, 10, 7, 4, 3, 3, 0, 0],
        [62, 20, 14, 8, 8, 11, 0, 0],
    ],
    columns=pd.MultiIndex.from_product(
        [("Q1", "Q2"), ("2021", "2022"), ("qty", "orders")]
    ),
    index=["January", "February", "March", "Totals"],
)

這是一種方法（使用來自 Python 標准庫的itertools模塊的產品，否則嵌套的 for 循環也是可能的）：

# Add new columns
for level1, level2 in product(["Q1", "Q2"], ["qty", "orders"]):
    df.loc[:, (level1, "subtotal", level2)] = (
        df.loc[:, (level1, "2021", level2)] + df.loc[:, (level1, "2022", level2)]
    )

# Sort columns
df = df.reindex(
    pd.MultiIndex.from_product(
        [("Q1", "Q2"), ("2021", "2022", "subtotal"), ("qty", "orders")]
    ),
    axis=1,
)

然后：

print(df)
# Output
           Q1                                      Q2                     \
         2021        2022        subtotal        2021        2022
          qty orders  qty orders      qty orders  qty orders  qty orders   
January    40      2    5      1       45      3    1      2    0      0   
February   20      8    2      3       22     11    4      6    0      0   
March       2     10    7      4        9     14    3      3    0      0   
Totals     62     20   14      8       76     28    8     11    0      0   


         subtotal
              qty orders  
January         1      2  
February        4      6  
March           3      3  
Totals          8     11