在python中使用numpy轻松添加两个数组? [英] Simple adding two arrays using numpy in python?

问题描述

这可能是一个简单的问题.但是，我想澄清以下代码的工作原理.

This might be a simple question. However, I wanted to get some clarifications of how the following code works.

a = np.arange(8)
a
array([1,2,3,4,5,6,7])
Example Function = a[0:-1]+a[1:]/2.0

在示例函数中，我想引起您注意数组a[0:-1]+a[1:]之间的加号.这是如何运作的?看起来像什么?

In the Example Function, I want to draw your attention to the plus sign between the array a[0:-1]+a[1:]. How does that work? What does that look like?

例如，加号(加法)是否添加了每个数组的第一个索引? (例如1+2)还是将所有内容加在一起? (例如1+2+2+3+3+4+4+5+5+6+6+7)

For instance, is the plus sign (addition) adding the first index of each array? (e.g 1+2) or add everything together? (e.g 1+2+2+3+3+4+4+5+5+6+6+7)

然后，我认为/2.0只是将其除以2 ...

Then, I assume /2.0 is just dividing it by 2...

推荐答案

一个numpy数组使用矢量代数，因为您只能在两个数组具有相同的维数时才添加两个数组

A numpy array uses vector algebra in that you can only add two arrays if they have the same dimensions as you are adding element by element

 a = [1,2,3,4,5]
 b = [1,1,1]
 a+b # will throw an error

白痴

 a = [1,2,3,4,5]
 b = [1,1,1,1,1]
 a+b # is ok

该划分也是逐元素进行的.

The division is also element by element.

现在您有关索引的问题

 a      = [1,2,3,4,5]
 a[0:-1]= [1,2,3,4]
 a[1:]  = [2,3,4,5]

或更普遍地a[index_start: index_end]在start_index处是包含性的，但在end_index中是排他性的-除非为您提供a[start_index:]，其中包括直到最后一个元素的所有内容.

or more generally a[index_start: index_end] is inclusive at the start_index but exclusive at the end_index - unless you are given a a[start_index:]where it includes everything up to and including the last element.

我的最后一个提示是尝试使用这些结构-尝试不同的东西没有任何危害，计算机不会在此处或此处以错误的值爆炸.当然，除非您尝试这样做.

My final tip is just to try and play around with the structures - there is no harm in trying different things, the computer will not explode with a wrong value here or there. Unless you trying to do so of course.

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