[FIXED] Why python allocate memory to string is different strategy?

Issue

String type uses Unicode representation. Unicode string can take up to 4 bytes per character depending on the encoding.

I have know python use three kinds of internal representations for Unicode string:

• 1 bytes
• 2 bytes
• 4 bytes

But still I am confused about memory allocation to the string.

import sys

>>> print(sys.getsizeof("hello world hello world"))
>>> 72

>>> print(sys.getsizeof(["hello world hello world"]))
>>> 64

>>> print(sys.getsizeof(("hello world hello world",)))
>>> 48

Why does this happen? When I put the same string into list and tuple the size were decreased. But why?

Solution

getsizeofcall is not recursive, and do not give you the size of all contained objects when you call it on a container. The only call to get the real str object size in your example is print(sys.getsizeof("hello world hello world")), the others just present you the size of a 1-item list, and the size of a 1 item tuple.

In order to get the full size of a composed object, you have to use a receipt for a recursive function that will yield you the size of an object, plus the size of all its attributes and contained objects if any.

Something along:

from sys import getsizeof

def getfullsize(obj, seen=None):
    if seen is None:
        seen = set()
    if id(obj) in seen:
        return 0
    seen.add(id(obj))
    size = getsizeof(obj)
    if not isinstance (obj, (str, bytes)) and hasattr(type(obj), "__len__"):
        for item in obj:
            if hasattr(type(obj), "values"):
                size += getfullsize(obj[item], seen)
           
            size += getfullsize(item, seen)
    if hasattr(obj, "__dict__"):
        size += getfullsize(obj.__dict__, seen)
    if hasattr(obj, "__slots__"):
        for attr in obj.__slots__:
            if (item:=getattr(obj, attr, None)) is not None:
                size+= getfullsize(item, seen)
    return size

Answered By - jsbueno