Practical Programming, 2nd Edition

Memory Addresses: How Python Keeps Track of Values

Back in ​Values, Variables, and Computer Memory​, you learned that Python keeps track of each value in a separate object and that each object has a memory address. You can discover the actual memory address of an object using built-in function id:

>>> help(id)
Help on built-in function id in module builtins:

id(...)
    id(object) -> integer

    Return the identity of an object.  This is guaranteed to be unique among
    simultaneously existing objects.  (Hint: it's the object's memory
    address.)

How cool is that? Let’s try it:

>>> id(-9)
4301189552
>>> id(23.1)
4298223160
>>> shoe_size = 8.5
>>> id(shoe_size)
4298223112
>>> fahrenheit ...