Python shared reference (multiple variable references) sample code

The code is as follows:

A = 3
b = A

First (Figure 1), you can see at a glance:

Variable name and object, after running assignment statement B = A, the variable A, a, is pointing to the memory space of object 3.
Assuming that a = ' python ' is executed at this point, a points to the string object you just created.
Let's try this situation again:

The code is as follows:

>>>list_1 = [1,2,3,4]
>>>list_2 = list_1
>>>list_2
>>>list_1[0] = ' python '
>>>list_2

Result

The code is as follows:

[1,2,3,4]
[' Python ', 2,3,4]

In my understanding, the list is a type object, and each element in the object can be regarded as a variable, referring to an object of different memory space list_1 = [1,2,3,4] is the memory space where list_1 points to the list, list_2 = List_1, They will point to the same memory space. When list_1[0] changes point, list_2 still points to the list object, so to see is to change the value of list_1[0], in fact, Python through the list_1 directly to the memory space to do the modification, list_2 point to no variables.
Maybe the result isn't what we want. If you do not want this to happen, you need a Python object copy instead of creating a reference.
Such as:

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