How does tuple unpacking differ from normal assignment? [duplicate]

Question

From this link I learnt that

The current implementation keeps an array of integer objects for all integers between -5 and 256, when you create an int in that range you actually just get back a reference to the existing object

But when I tried to give some example for my session and I found out that it behaves differently with assignment and tuple unpacking.

Here is the snippet:

>>> a,b = 300,300
>>> a is b
True
>>> c = 300
>>> d = 300
>>> c is d
False

Answer 1

Because int is immutable, Python may or may not use exists object, if you save the following code in to a script file, and run it, it will output two True.

a, b = 300, 300
print a is b

c = 300
d = 300
print c is d

When Python compile the code, it may reuse all the constants. Becasue you input your code in a python session, the codes are compiled line by line, Python can't reuse all the constants as one object.

The document only says that there will be only one instance for -5 to 256, but doesn't define the behavior of others. For immutable types, is and is not is not important, because you can't modify them.