如何在NumPy数组中添加额外的列 [英] How to add an extra column to a NumPy array

问题描述

假设我有一个NumPy数组，a:

Let’s say I have a NumPy array, a:

a = np.array([
    [1, 2, 3],
    [2, 3, 4]
    ])

我想添加一列零以获取数组，b:

And I would like to add a column of zeros to get an array, b:

b = np.array([
    [1, 2, 3, 0],
    [2, 3, 4, 0]
    ])

如何在NumPy中轻松地做到这一点?

How can I do this easily in NumPy?

推荐答案

我认为更简单，启动更快捷的解决方案是执行以下操作:

I think a more straightforward solution and faster to boot is to do the following:

import numpy as np
N = 10
a = np.random.rand(N,N)
b = np.zeros((N,N+1))
b[:,:-1] = a

时间:

In [23]: N = 10

In [24]: a = np.random.rand(N,N)

In [25]: %timeit b = np.hstack((a,np.zeros((a.shape[0],1))))
10000 loops, best of 3: 19.6 us per loop

In [27]: %timeit b = np.zeros((a.shape[0],a.shape[1]+1)); b[:,:-1] = a
100000 loops, best of 3: 5.62 us per loop

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