Python:[]在这里的含义是什么? [英] Python: What does the use of [] mean here?

问题描述

这两个在python中的语句有什么区别?

What is the difference in these two statements in python?

var = foo.bar

和

var = [foo.bar]

我认为这使var成为包含foo.bar的列表，但是我不确定.另外，如果这是行为，并且foo.bar已经是列表，您在每种情况下会得到什么?

I think it is making var into a list containing foo.bar but I am unsure. Also if this is the behavior and foo.bar is already a list what do you get in each case?

例如:如果foo.bar = [1、2]，我会得到这个吗?

For example: if foo.bar = [1, 2] would I get this?

var = foo.bar #[1, 2]

和

var = [foo.bar] #[[1,2]] where [1,2] is the first element in a multidimensional list

推荐答案

[]是一个空列表.

[foo.bar]正在创建一个新列表([])，其中foo.bar作为列表中的第一项，然后可以通过其索引进行引用:

[foo.bar] is creating a new list ([]) with foo.bar as the first item in the list, which can then be referenced by its index:

var = [foo.bar]
var[0] == foo.bar # returns True 

因此，您猜测foo.bar = [1,2]的分配是完全正确的.

So your guess that your assignment of foo.bar = [1,2] is exactly right.

如果您还没有的话，我建议您在Python交互式解释器中尝试这种事情.这很容易:

If you haven't already, I recommend playing around with this kind of thing in the Python interactive interpreter. It makes it pretty easy:

>>> []
[]
>>> foobar = [1,2]
>>> foobar
[1, 2]
>>> [foobar]
[[1, 2]]

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