Python code keeps duplicating information - OOP ( Could be related to shallow copy? )

[ben1122]

never mind, asked a friend.

[DeaD_EyE]

No, Python doesn't duplicate objects if you mean the connection between classes <> Instances.

Example:

from sys import getsizeof

class Foo:
    pass


print(f"Class        -> {getsizeof(Foo)}")
print(f"Foo-Instance -> {getsizeof(Foo())}")

Output:
Class        -> 1072
Foo-Instance -> 48

(Python 3.10.4)
As we can see, the instance needs only 48 bytes in memory. The instance has a reference to the class Foo, which is only once in memory. The class Foo itself consumes much more memory because the whole logic is done there.

To make the class and the resulting instance smaller, you could use __slots__.

from sys import getsizeof

class Foo:
    __slots__ = ()


print(f"Class        -> {getsizeof(Foo)}")
print(f"Foo-Instance -> {getsizeof(Foo())}")

Output:
Class        -> 904
Foo-Instance -> 32

Python preallocates integers from -5 to 256. If the code uses one of these values, they exist only once in memory.

r = range(-10, 260)
for a, b in zip(r,r):
    if a is not b:
        print(a)

Output:
-10
-9
-8
-7
-6
257
258
259

The printed numbers are outside the range of preallocated integers.
Those integers, which are printed, are copies. They exist twice for a short time in memory, until the garbage collection deletes the objects after they are no longer required.

Another example: Modules
If you import a module, its content is parsed, executed and cached in sys.modules.
Importing the module again, will use the already imported module from cache.

Python does much to reduce the memory footprint, but in general, a dynamic Language consumes more memory as a compiled language.