2个列表之间的相乘 [英] Multiplication between 2 lists

问题描述

我有2个列表

a=[[2,3,5],[3,6,2],[1,3,2]]
b=[4,2,1]

我希望输出为:

c=[[8,12,20],[6,12,4],[1,3,2]]

目前我正在使用以下代码，但是它的问题是计算时间非常长，因为列表中的值数量很大.列表的第一个列表有1000个列表，其中每个列表有10000个值，并且第二个列表有1000个值，因此计算时间是一个问题.我想要一个新的想法，其中计算时间更少.当前代码为:

At present i am using the following code but its problem is that the computation time is very high as the number of values in my list are very large.The first list of list has 1000 list in which each list has 10000 values and the second list has 1000 values.Therefore the computation time is a problem.I want a new idea in which computation time is less.The present code is:

a=[[2,3,5],[3,6,2],[1,3,2]]
b=[4,2,1]
c=[]
s=0
for i in b:
    c1=[]
    t=0
    s=s+1
    for j in a:
        t=t+1
        for k in j:
            if t==s:
                m=i*k
                c1.append(m)
    c.append(c1)
print(c)

推荐答案

您可以使用numpy:

You can use numpy :

>>> import numpy as np
>>> a=np.array([[2,3,5],[3,6,2],[1,3,2]])
>>> b=np.array([4,2,1])

>>> a*np.vstack(b)
array([[ 8, 12, 20],
       [ 6, 12,  4],
       [ 1,  3,  2]])

或者像@ csunday95建议的那样，它是一种更优化的方式，您可以使用转置而不是vstack:

Or as @csunday95 suggested as a more optimized way you can use transpose instead of vstack :

>>> (a.T*b).T 
array([[ 8, 12, 20],
       [ 6, 12,  4],
       [ 1,  3,  2]])

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