Measure Object Size Accurately in Python - Sys.GetSizeOf not functioning

Question

I am trying to accurately/definitively find the size differences between two different classes in Python. They are both new style classes, save for one not having sl

Answer 1

The following function has been tested in Python 3.6, 64bit system. It has been very useful to me. (I picked it up off the internet and tweaked it to my style, and added the use of 'slots' feature. I am unable to find the original source again.)

def getSize(obj, seen: Optional[Set[int]] = None) -> int:
  """Recursively finds size of objects. Needs: import sys """
  seen = set() if seen is None else seen

  if id(obj) in seen: return 0  # to handle self-referential objects
  seen.add(id(obj))

  size = sys.getsizeof(obj, 0) # pypy3 always returns default (necessary)
  if isinstance(obj, dict):
    size += sum(getSize(v, seen) + getSize(k, seen) for k, v in obj.items())
  elif hasattr(obj, '__dict__'):
    size += getSize(obj.__dict__, seen)
  elif hasattr(obj, '__slots__'): # in case slots are in use
    slotList = [getattr(C, "__slots__", []) for C in obj.__class__.__mro__]
    slotList = [[slot] if isinstance(slot, str) else slot for slot in slotList]
    size += sum(getSize(getattr(obj, a, None), seen) for slot in slotList for a in slot)
  elif hasattr(obj, '__iter__') and not isinstance(obj, (str, bytes, bytearray)):
    size += sum(getSize(i, seen) for i in obj)
  return size

Now for the objects of the following classes,

class test3(object):
    def __init__(self):
        self.one = 1
        self.two = "two variable"

class test4(object):
    __slots__ = ('one', 'two')
    def __init__(self):
        self.one = 1
        self.two = "two variable"

the following results are obtained,

In [21]: t3 = test3()

In [22]: getSize(t3)
Out[22]: 361

In [23]: t4 = test4()

In [25]: getSize(t4)
Out[25]: 145

Feedbacks to improve the function are most welcome.