Question

代码：

from functools import reduce

num = 2989

numSplit = [int(x) for x in str(num)]
# convert the number to a list with each digit separated

numProduct = reduce((lambda x,y: x*y), numSplit)
# uses reduce to multiply each number in order

print(numProduct)

问题：

使用NumProduct，我试图找到2*9，9*8和8*9的单独产品。

我不确定如何修改lambda以仅查找[2,9,8,9]中的数字对（或其他各种长度）的乘积。需要协助。 Tnx。

Answer 1

Reduce()会将整个可迭代项减少为一个值-这不是您想要的。相反，可以考虑将相邻的值分组，然后在每个组中采用乘积。

num = 2989

numSplit = [int(x) for x in str(num)]
numProduct = [x * y for x, y in zip(numSplit, numSplit[1:])]

我在这里zip numSplit的列表中，numSplit的一个切片偏移了一个，以将每个数字与其右边的邻居分组。然后，我对此进行迭代，将两个值相乘。如果一个列表比另一个列表短，则zip会将所有列表都截短为最短的长度-这就是这里发生的情况，从而防止在末尾出现多余的项。

结果：

>>> numProduct
[18, 72, 72]

更新

如果要支持任意大小的分组，请使用以下内容：

from functools import reduce
from operator import mul

num = 2989
size = 3

numSplit = [int(x) for x in str(num)]
numProduct = [reduce(mul, p) for p in zip(*(numSplit[x:] for x in range(size)))]

结果：

>>> numProduct
[144, 648]

Answer 2

如果您确实想要，可以在此处使用reduce。

if object_id('ForSubQuery') is not null begin
    DROP TABLE ForSubQuery
end
Create Table ForSubQuery
(   
    SecID int
)

INSERT INTO ForSubQuery SELECT 123
INSERT INTO ForSubQuery SELECT 234

GO

SELECT * FROM ForSubQuery

if object_id('MainTable') is not null begin
    DROP TABLE MainTable
end
Create Table MainTable
(   
    IsPrior bit,
    IsCurrent bit,
    IsIdeal bit,
    [SecurityID] int,
    PosID int
)

INSERT INTO MainTable SELECT 1,1,1,123,1
INSERT INTO MainTable SELECT 0,1,1,234,2
INSERT INTO MainTable SELECT 1,0,0,234,3

GO

SELECT * FROM MainTable

SELECT 
       CASE
            WHEN
                Position.IsPrior = 1
                AND Position.[SecurityID] in (SELECT
                SecID
                FROM ForSubQuery
                )               
                 THEN 1
            ELSE 0
        END AS IsPriorAfter
       ,CASE
            WHEN
                Position.IsIdeal = 1
                AND [Position].[SecurityID] IN (SELECT
                        secid
                FROM ForSubQuery            
                    )
                 THEN 1
            ELSE 0
        END AS IsIdealAfter 
     ,CASE
            WHEN
                Position.IsCurrent = 1
                AND [Position].[SecurityID] IN (SELECT
                        secid
                FROM ForSubQuery
                    )
                 THEN 1
            ELSE 0
        END AS IsCurrentAfter
    , Position.*
    FROM MainTable [Position]
    order by Position.PosID

使lambda查找数字对的乘积

2 个答案: