A million objects: where do the bytes go?
Say you’re simulating a forest: a million trees, each with a position and an age. class Tree: def __init__(self, x, y, age): self.x = x self.y = y self.age = age Three small ints per tree. In C that’s 12–24 bytes a tree, so a million trees would take about 24 MB. In Python 3.10 the same million trees take 152 MB. In 3.13 they take 96 MB, without changing a line. There are two ways to make a million objects cheap: make each object smaller, or make fewer objects. This post is about the first one. It covers where those bytes go, what __slots__ removes, and how much of that CPython 3.11+ now does for you. ...