numpy数组中的列表列表

How do I convert a simple list of lists into a numpy array? The rows are individual sublists and each row contains the elements in the sublist.

如何将简单的列表列表转换为numpy数组？行是单个子列表，每行包含子列表中的元素。

5 个解决方案

#1

If your list of lists contains lists with varying number of elements then the answer of Ignacio Vazquez-Abrams will not work. Instead there are 3 options:

如果您的列表列表包含具有不同数量元素的列表，则Ignacio Vazquez-Abrams的答案将不起作用。相反，有3个选项：

1) Make an array of arrays:

1）创建一个数组数组：

x=[[1,2],[1,2,3],[1]]
y=numpy.array([numpy.array(xi) for xi in x])
type(y)
>>><type 'numpy.ndarray'>
type(y[0])
>>><type 'numpy.ndarray'>

2) Make an array of lists:

2）制作一系列清单：

x=[[1,2],[1,2,3],[1]]
y=numpy.array(x)
type(y)
>>><type 'numpy.ndarray'>
type(y[0])
>>><type 'list'>

3) First make the lists equal in length:

3）首先使列表的长度相等：

x=[[1,2],[1,2,3],[1]]
length = len(sorted(x,key=len, reverse=True)[0])
y=numpy.array([xi+[None]*(length-len(xi)) for xi in x])
y
>>>array([[1, 2, None],
>>>       [1, 2, 3],
>>>       [1, None, None]], dtype=object)

#2

>>> numpy.array([[1, 2], [3, 4]]) 
array([[1, 2], [3, 4]])

#3

As this is the top search on Google for converting a list of lists into a Numpy array, I'll offer the following despite the question being 4 years old:

由于这是谷歌将列表列表转换为Numpy阵列的最佳搜索，我将提供以下内容，尽管问题是4年前：

>>> x = [[1, 2], [1, 2, 3], [1]]
>>> y = numpy.hstack(x)
>>> print(y)
[1 2 1 2 3 1]

When I first thought of doing it this way, I was quite pleased with myself because it's soooo simple. However, after timing it with a larger list of lists, it is actually faster to do this:

当我第一次想到这样做时，我对自己很满意，因为它太简单了。但是，在使用更大的列表列表对其进行计时后，实际上执行此操作会更快：

>>> y = numpy.concatenate([numpy.array(i) for i in x])
>>> print(y)
[1 2 1 2 3 1]

Note that @Bastiaan's answer #1 doesn't make a single continuous list, hence I added the concatenate.

请注意，@ Bastiaan的答案＃1没有一个连续的列表，因此我添加了连接。

Anyway...I prefer the hstack approach for it's elegant use of Numpy.

无论如何......我更喜欢hstack方法，因为它优雅地使用了Numpy。

#4

It's as simple as:

它很简单：

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

#5

Again, after searching for the problem of converting nested lists with N levels into an N-dimensional array I found nothing, so here's my way around it:

再次，在搜索了将N级别的嵌套列表转换为N维数组的问题后，我什么也没找到，所以这是我的方法：

import numpy as np

new_array=np.array([[[coord for coord in xk] for xk in xj] for xj in xi], ndmin=3) #this case for N=3

#1