Get Size of a Dictionary - Python

We are given a dictionary in Python and our task is to find the memory size that the dictionary occupies. This can be important when you need to know how much memory your data structures are consuming especially for large dictionaries. For example, if we have a dictionary like this: {'a': 1, 'b': 2, 'c': 3}, we need to determine how much memory this dictionary takes up in the system.

Using sys.getsizeof()

sys module in Python provides a function called getsizeof() which returns the size of an object in bytes. This is the most straightforward way to determine the memory usage of a dictionary but keep in mind that getsizeof() only gives the immediate size of the dictionary object and does not account for the memory used by the objects the dictionary refers to (e.g., the keys and values).

import sys

d1 = {'a': 1, 'b': 2, 'c': 3}

# Getting the size of the dictionary in bytes
size = sys.getsizeof(d1)

print(size)

184

Explanation:

• sys.getsizeof(d1) returns the memory size of the dictionary d1 in bytes.
• number 184 is an example and it could vary depending on the dictionary contents and system architecture.

Using __sizeof__() Method

Python also has an inbuilt __sizeof__() method to determine the space allocation of an object without any additional garbage value. It has been implemented in the below example.

d1 = {'a': 1, 'b': 2, 'c': 3}

# Getting the size of the dictionary using __sizeof__()
size = d1.__sizeof__()

print(size)

168

Explanation:

• d1.__sizeof__() directly returns the memory size of the dictionary object d1 in bytes.
• This method only measures the immediate memory usage of the dictionary object and does not account for the memory usage of its keys and values.

Using pympler.asizeof

pympler library is a third-party Python library that provides more accurate memory usage measurements compared to sys.getsizeof(). The asizeof module in pympler can handle complex objects and nested data structures much more effectively including dictionaries, lists and other objects. It returns the full memory consumption, including the memory used by the elements the dictionary contains.

#pip install pympler

from pympler import asizeof

d1 = {'a': 1, 'b': 2, 'c': {'nested_key': [1, 2, 3]}}

# Getting the total memory size of the dictionary, including nested objects
size = asizeof.asizeof(d1)

print(size)

Output:

752

Explanation:

• asizeof.asizeof(d1) calculates the memory consumption of the entire dictionary, including nested structures.
• The pympler library can provide more accurate results for complex objects by considering the entire object tree (i.e., keys, values, and their references).