Python：替换列表列表中的元素（#2）

发布于 2024-09-25 20:14:34 字数 556 浏览 3 评论 0原文

上一个与我的标题相同的问题已发布，（我认为）有同样的问题，但代码中有其他问题。我无法确定那个案例是否与我的相同。

无论如何，我想替换列表中列表中的元素。代码：

myNestedList = [[0,0]]*4 # [[0, 0], [0, 0], [0, 0], [0, 0]]
myNestedList[1][1] = 5

我现在期望：

[[0, 0], [0, 5], [0, 0], [0, 0]]

但我得到：

[[0, 5], [0, 5], [0, 5], [0, 5]]

为什么？

这在命令行中复制。 Python 3.1.2（r312:79147，2010 年 4 月 15 日，15:35:48） [GCC 4.4.3] 在 linux2 上

原文

A previous question with the same title as mine has been posted, with (I think) the same question, but had other problems in the code. I was not able to determine if that case was identical to mine or not.

Anyway, I want to replace an element within a list in a list.
Code:

myNestedList = [[0,0]]*4 # [[0, 0], [0, 0], [0, 0], [0, 0]]
myNestedList[1][1] = 5

I now expect:

[[0, 0], [0, 5], [0, 0], [0, 0]]

But I get:

[[0, 5], [0, 5], [0, 5], [0, 5]]

Why?

This is replicated in the command line.
Python 3.1.2 (r312:79147, Apr 15 2010, 15:35:48)
[GCC 4.4.3] on linux2

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

×纯※雪 2024-10-02 20:14:34

您通过 * 4 对同一对象有四个引用，请使用带有范围的列表理解来进行计数：

my_nested_list = [[0,0] for count in range(4)]
my_nested_list[1][1] = 5
print(my_nested_list)

为了更具体地解释问题：

yourNestedList = [[0,0]]*4
yourNestedList[1][1] = 5
print('Original wrong: %s' % yourNestedList)

my_nested_list = [[0,0] for count in range(4)]
my_nested_list[1][1] = 5
print('Corrected: %s' % my_nested_list)

# your nested list is actually like this
one_list = [0,0]
your_nested_list = [ one_list for count in range(4) ]
one_list[1] = 5
print('Another way same: %s' % your_nested_list)

You are having four references to same object by * 4, use instead list comprehension with range for counting:

my_nested_list = [[0,0] for count in range(4)]
my_nested_list[1][1] = 5
print(my_nested_list)

To explain little more concretely the problem:

yourNestedList = [[0,0]]*4
yourNestedList[1][1] = 5
print('Original wrong: %s' % yourNestedList)

my_nested_list = [[0,0] for count in range(4)]
my_nested_list[1][1] = 5
print('Corrected: %s' % my_nested_list)

# your nested list is actually like this
one_list = [0,0]
your_nested_list = [ one_list for count in range(4) ]
one_list[1] = 5
print('Another way same: %s' % your_nested_list)

回复收藏 0 原文

~没有更多了~