两个二维列表的按元素乘积 [英] Element-wise product of two 2-D lists

问题描述

我不能使用Numpy或任何其他库函数，因为这是我必须要做的问题，我必须定义自己的方式.

I can't use Numpy or any other library function as this is a question I have to do, I have to define my own way.

我正在编写一个以两个列表(二维)为参数的函数.该函数应计算两个列表的元素乘积，并将它们存储在第三个列表中，然后从函数返回此结果列表. 输入列表的示例为:

I am writing a function that takes two lists (2 dimensional) as arguments. The function should calculate the element-wise product of both lists and store them in a third list and return this resultant list from the function. An example of the input lists are:

[[2,3,5,6,7],[5,2,9,3,7]]  

list2:

[[5,2,9,3,7],[1,3,5,2,2]]

该函数将打印以下列表:

The function prints the following list:

[[10, 6, 45, 18, 49], [5, 6, 45, 6, 14]] 

即2*5=10，3*2=6，5*9=45 ...等.

这是我的下面代码，但仅适用于其中包含2个列表(元素)的列表，就像上面的示例一样，并且效果很好，但是我想要编辑我的代码，以便无论如何2-D列表中有许多列表(元素)，它应该在新的2-D列表中打印出其按元素的乘积，例如它也应该适用于

This is my code below, but it is only for a list with 2 lists (elements) inside in it like the example above and works perfectly fine for that, but what I want is to edit my code so that no matter how many number of lists (elements) are there in the 2-D list, it should print out its element-wise product in a new 2-D list e.g. it should also work for

[[5,2,9,3,7],[1,3,5,2,2],[1,3,5,2,2]]

或

[[5,2,9,3,7],[1,3,5,2,2],[1,3,5,2,2],[5,2,9,3,7]]

或整个列表中有任意数量的列表.

or any number of lists there are within the whole list.

def ElementwiseProduct(l,l2):
    i=0
    newlist=[] #create empty list to put prouct of elements in later
    newlist2=[]
    newlist3=[] #empty list to put both new lists which will have proudcts in them
    while i==0:
        a=0
        while a<len(l[i]):
            prod=l[i][a]*l2[i][a] #corresponding product of lists elements
            newlist.append(prod) #adding the products to new list
            a+=1
        i+=1
    while i==1:
        a=0
        while a<len(l[i]):
            prod=l[i][a]*l2[i][a] #corresponding product of lists elements
            newlist2.append(prod) #adding the products to new list
            a+=1
        i+=1
    newlist3.append(newlist)
    newlist3.append(newlist2)
    print newlist3

#2 dimensional list example
list1=[[2,3,5,6,7],[5,2,9,3,7]] 
list2=[[5,2,9,3,7],[1,3,5,2,2]]  
ElementwiseProduct(list1,list2)

推荐答案

您可以 zip 列表理解中的两个列表，然后进一步 zip 生成的子列表，然后最后将各项相乘:

You can zip the two lists in a list comprehension, then further zip the resulting sublists and then finally multiply the items:

list2 = [[5,2,9,3,7],[1,3,5,2,2]]
list1 = [[2,3,5,6,7],[5,2,9,3,7]]

result = [[a*b for a, b in zip(i, j)] for i, j in zip(list1, list2)]
print(result)
# [[10, 6, 45, 18, 49], [5, 6, 45, 6, 14]]

如果列表/子列表的元素数量不同，则

Should in case the lists/sublists do not have the same number of elements, itertools.izip_longest can be used to generate fill values such as an empty sublist for the smaller list, or 0 for the shorter sublist:

from itertools import izip_longest

list1 = [[2,3,5,6]]
list2 = [[5,2,9,3,7],[1,3,5,2,2]]
result = [[a*b for a, b in izip_longest(i, j, fillvalue=0)] 
               for i, j in izip_longest(list1, list2, fillvalue=[])]
print(result)
# [[10, 6, 45, 18, 0], [0, 0, 0, 0, 0]]

您可以将内部fillvalue从0更改为1，以按原样返回较长子列表中的元素，而不是同质0.

You may change the inner fillvalue from 0 to 1 to return the elements in the longer sublists as is, instead of a homogeneous 0.

参考:

列表理解

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