英文:
How to extract specific elements from a nested list in Python?
问题
我有一个Python中的嵌套列表，其中每个元素也是一个列表。我想根据某些条件从这个嵌套列表中提取特定的元素。例如，假设我有以下嵌套列表：
my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
我想提取每个内部列表中索引为1的所有元素，结果应为[2, 5, 8]。
在Python中，有什么有效的方法可以实现这一点？是否有任何内置的函数或方法可以帮助简化这个过程？非常感谢任何见解或代码示例。谢谢！
根据我的尝试，我期望提取的元素列表应包含每个内部列表中索引为1的元素，即[2, 5, 8]。然而，我没有得到期望的输出。
请问是否有人能指出我可能做错了什么，或者建议一个成功从嵌套列表中提取特定元素的替代方法？非常感谢您提前的帮助！
英文:
I have a nested list in Python, where each element is also a list. I would like to extract specific elements from this nested list based on certain conditions. For example, let's say I have the following nested list:
my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
I want to extract all the elements at index 1 from each inner list, resulting in the output [2, 5, 8].
What would be an efficient way to achieve this in Python? Are there any built-in functions or methods that can help simplify this process? Any insights or code examples would be greatly appreciated. Thank you!
Based on my attempt, I expected the extracted_elements list to contain the elements at index 1 from each inner list, which would be [2, 5, 8]. However, I'm not getting the desired output.
Could someone please point out what I might be doing wrong or suggest an alternative approach to successfully extract the specific elements from the nested list? Thank you in advance for your help!
答案1
得分: 1
你可以使用一个 列表推导式 轻松完成这个任务：
my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
result = [sublist[1] for sublist in my_list]
英文:
You can do this easily enough with a list comprehension
my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
result = [sublist[1] for sublist in my_list]
答案2
得分: 1
你可以使用NumPy数组 https://numpy.org/doc/stable/user/basics.indexing.html
import numpy as np
my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
np_array = np.array(my_list)
np_array[:, 1] # 返回第二列
array([2, 5, 8])
英文:
You can use numpy array https://numpy.org/doc/stable/user/basics.indexing.html
>>> import numpy as np
>>> my_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
>>> np_array = np.array(my_list)
>>> np_array[:,1] # returns the second column
array([2, 5,8])`
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