How to manually calculate a size of a dictionary (number of bytes it occupies in memory). I read that initially it is 280 bytes, at 6th key it increases and then at 86th so on. I want to calculate the size it will occupy when I have more than 10000 keys.
4 Answers
sys.getsizeof will help in that case:
from sys import getsizeof dct = {'a': 5, 'b': 7} print(getsizeof(dct)) especially for dictionaries the size will depend on your python version (the implementation has changed recently).
a quick way to create an N-sized dictionary is:
from itertools import zip_longest dct = dict(zip_longest(range(N), (), fillvalue=None)) # {0: None, 1: None, 2: None, ....} this should help test your assumptions for your specific python version.
this question may be related.
the sys.getsizeof not work with nested dict, as shown in the example bellow.
>>> import sys >>> d = { "onj1": {"name":"object 01", "id": "123"},"onj2": {"name":"object 02", "id": "124"}} >>> d0 = {} >>> sys.getsizeof(d0) 240 >>> sys.getsizeof(d) 240 So the solution found was the function provided by this site:post OR github
follow the function:
import sys def get_size(obj, seen=None): """Recursively finds size of objects""" size = sys.getsizeof(obj) if seen is None: seen = set() obj_id = id(obj) if obj_id in seen: return 0 # Important mark as seen *before* entering recursion to gracefully handle # self-referential objects seen.add(obj_id) if isinstance(obj, dict): size += sum([get_size(v, seen) for v in obj.values()]) size += sum([get_size(k, seen) for k in obj.keys()]) elif hasattr(obj, '__dict__'): size += get_size(obj.__dict__, seen) elif hasattr(obj, '__iter__') and not isinstance(obj, (str, bytes, bytearray)): size += sum([get_size(i, seen) for i in obj]) return size You can do a quick check with sys.getsizeof() (it will return the size of an object in bytes):
>>> import sys, itertools >>> sys.getsizeof(dict(zip(range(1), itertools.cycle([1])))) 280 >>> sys.getsizeof(dict(zip(range(5), itertools.cycle([1])))) 280 >>> sys.getsizeof(dict(zip(range(6), itertools.cycle([1])))) 1048 >>> sys.getsizeof(dict(zip(range(85), itertools.cycle([1])))) 3352 >>> sys.getsizeof(dict(zip(range(86), itertools.cycle([1])))) 12568 >>> sys.getsizeof(dict(zip(range(87), itertools.cycle([1])))) 12568 >>> sys.getsizeof(dict(zip(range(10000), itertools.cycle([1])))) 786712 If you are interested in actual inner-workings of Python dictionaries, the dictobject.c is the definitive resource (here for the latest Python 3.6 branch). Also, take a look at dictnotes.txt.
Use sys.getsizeof to get the size info
