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]

Chris Angelico 在 2021年6月15日 星期二上午5:23:12 [UTC+8] 的信中寫道：
> On Tue, Jun 15, 2021 at 7:11 AM Rob Cliffe via Python-list 
> <pytho... at python.org> wrote: 
> > 
> > This puzzled me, so I played around with it a bit (Python 3.8.3): 
> > 
> > n = [] 
> > for i in range(3): 
> > n.append((1,7,-3,None,"x")) 
> > for i in range(3): 
> > n.append((1,7,-3,None,"x")) 
> > print([id(x) for x in n]) 
> > 
> > a = 4 
> > n = [] 
> > for i in range(3): 
> > n.append((1,7,-3,a,None,"x")) 
> > for i in range(3): 
> > n.append((1,7,-3,a,None,"x")) 
> > print([id(x) for x in n]) 
> > 
> > Output: 
> > 
> > [27164832, 27164832, 27164832, 27164832, 27164832, 27164832] 
> > [30065208, 30065496, 30237192, 30239976, 30240024, 30343928] 
> > 
> > Evidently the compiler is clever enough to pick out a constant tuple and 
> > create (or cause to get created) a single instance of it which is used 
> > when required. Indeed disassembling the code shows that LOAD_CONST is 
> > used to get the tuple. But it obviously can't do that when the tuple 
> > contains a variable.
> Correct. In theory, Python could intern the tuples (as can be done 
> with strings), noticing that it's constructing one that is identical 
> to one it already has, but the effort of doing that is hard to 
> justify. Simpler to just build a brand new tuple every time. 
> 
> ChrisA
>From a user's point, I don't really care how Python creates those instances, 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:-)

--Jach