对numpy数组进行的操作包含大小不同的行

问题描述

我有两个列表，看起来像这样:

I have two lists, looking like this:

a= [[1,2,3,4], [2,3,4,5],[3,4,5,6,7]], b= [[5,6,7,8], [9,1,2,3], [4,5,6,7,8]]

我想逐个元素地相互减去以得到这样的输出:

which I want to subtract from each other element by element for an Output like this:

a-b= [[-4,-4,-4,-4],[7,2,2,2],[-1,-1,-1,-1,-1]]

为此，我将每个 a 和 b 都转换为数组，并减去它们，我使用:

In order to do so I convert each of a and b to arrays and subtract them I use:

np.array(a)-np.array(b)

输出只会给我错误:

我做错了什么? np.array 命令是否应确保转换为数组?

What am I doing wrong? Shouldn't the np.array command ensure the conversion to the array?

推荐答案

您可以尝试:

>>> a= [[1,2,3,4], [2,3,4,5],[3,4,5,6,7]]
>>> b= [[5,6,7,8], [9,1,2,3], [4,5,6,7,8]]
>>> 
>>> c =[]
>>> for i in range(len(a)):
    c.append([A - B for A, B in zip(a[i], b[i])])


>>> print c
[[-4, -4, -4, -4], [-7, 2, 2, 2], [-1, -1, -1, -1, -1]]

或者第二种方法是使用地图:

Or 2nd method is using map:

from operator import sub
a= [[1,2,3,4], [2,3,4,5],[3,4,5,6,7]]
b= [[5,6,7,8], [9,1,2,3], [4,5,6,7,8]]
c =[]
for i in range(len(a)):
    c.append(map(sub, a[i], b[i]))  
print c
[[-4, -4, -4, -4], [-7, 2, 2, 2], [-1, -1, -1, -1, -1]]

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