Why the list creates in two different ways? Does it cause by the mutability of its elements? Where the Python document explains it?

[Jach Feng]

Greg Ewing 在 2021年6月16日 星期三上午7:11:35 [UTC+8] 的信中寫道：
> On 15/06/21 7:32 pm, Jach Feng wrote: 
> > But usually the list creation is not in simple way:-) for example: 
> >>>> a = [1,2] 
> >>>> m = [a for i in range(3)] 
> >>>> m 
> > [[1, 2], [1, 2], [1, 2]] 
> >>>> id(m[0]) == id(m[1]) == id(m[2]) 
> > True
> The first line is only executed once, so you just get one 
> list object [1, 2]. You then refer to that object three times 
> when you build the outer list. 
> 
> To get three different [1, 2] lists you would need something 
> like this:
> m = [[1,2] for i in range(3)]
> This executes the [1, 2] expression 3 times. Because lists are 
> mutable, you can be sure that this will give you 3 distinct 
> list objects. 
> 
> -- 
> Greg
Yes, I know. Here I just want to show another gutter I had found:-). Anyone else?

--Jach