CODEWITHSUNDEEP
pythonpython-3.xpython-2.7booleansizeof
msc
msc

Reputation: 34638

getsizeof() function returns different output in Python 2 and Python 3

Small code:

import sys

x = True

print(sys.getsizeof(x))

Python 2 output:

24

Python 3 output:

28

Why does outputs of getsizeof() function different in Python 2 and Python 3?

Upvotes: 3

Views: 267

Answers (2)

Acorn
Acorn

Reputation: 26166

For built-in types, sys.getsizeof() returns basically an implementation detail of the Python implementation you are using.

This means that, even for the same Python version, you might see different sizes for different implementations/platforms/builds... Therefore, you cannot rely on specific answers – and much less expect them to stay constant!

Finally, note that sys.getsizeof() is not an operator; it is simply a function of the sys module.

Upvotes: 3

user2357112
user2357112

Reputation: 281476

On both Python 2 and Python 3, bool is a subclass of int, and True == 1. However, on Python 3, int is the equivalent of Python 2 long, and it stores integers in an arbitrary-precision representation.

On the build of Python 3 you're running, that representation happens to take 4 more bytes to store the value 1 than what the int representation takes on your Python 2 build, most likely due to the ob_size field that stores the length of the arbitrary-precision representation.

If this ever actually matters to a program you write, you're probably doing something really crazy, and/or misusing getsizeof.

Upvotes: 3

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