How to know bytes size of python object like arrays and dictionaries? - The simple way

Question

I was looking for a easy way to know bytes size of arrays and dictionaries object, like

[ [1,2,3], [4,5,6] ] or { 1:{2:2} }

Many topics say to use pylab, for example:

from pylab import *

A = array( [ [1,2,3], [4,5,6] ] )
A.nbytes
24

But, what about dictionaries? I saw lot of answers proposing to use pysize or heapy. An easy answer is given by Torsten Marek in this link: Which Python memory profiler is recommended?, but I haven't a clear interpretation about the output because the number of bytes didn't match.

Pysize seems to be more complicated and I haven't a clear idea about how to use it yet.

Given the simplicity of size calculation that I want to perform (no classes nor complex structures), any idea about a easy way to get a approximate estimation of memory usage of this kind of objects?

Kind regards.

Answer 1

There's:

>>> import sys
>>> sys.getsizeof([1,2, 3])
96
>>> a = []
>>> sys.getsizeof(a)
72
>>> a = [1]
>>> sys.getsizeof(a)
80

But I wouldn't say it's that reliable, as Python has overhead for each object, and there are objects that contain nothing but references to other objects, so it's not quite the same as in C and other languages.

Have a read of the docs on sys.getsizeof and go from there I guess.