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15日 星期二下午3:01:46 [UTC+8] 的信中寫道：
> On 15/06/21 3:18 pm, Jach Feng wrote: 
> > From a user's point, I don't really care how Python creates thoseinstances, > either using an already exist one or create a new one, as
> > long as each element (and its sub-element) are independent from each 
> > other so a modification of one will not influence the other. The real 
> > problem is there are different methods can be used to build it and some 
> > will fail in this purpose. The * operator is one of them, but anyone 
> > else? I really like to know:-)
> This really has nothing to do with how the tuples are created. 
> It all depends on what you choose to put in them. 
> 
> When you use square brackets to build a list, you can be sure that 
> it will create a new list object each time. 
> 
> Also, if you create two tuples, by any means, containing distinct 
> elements, you can be sure that you will get two distinct tuple 
> objects. 
> 
> So, if you do this: 
> 
> a = [1, 2] 
> b = [1, 2] 
> c = [1, 2] 
> d = [1, 2] 
> 
> s = (a, b) 
> t = (c, d) 
> 
> then you are guaranteed to get four different list objects and 
> two diffferent tuple objects. 
> 
> Does that help to ease your fears? 
> 
> -- 
> Greg
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

--Jach