Python __slots__: cut instance memory by 40–60% without changing your logic
By default, Python allocates a __dict__ for every instance of a class. Flexible, yes. Cheap, no. When you hold thousands or millions of objects in memory at once, that dictionary overhead adds up fast. __slots__ removes it and replaces per-instance storage with compact internal descriptors. Typical result: 40 to 60 percent less memory per instance. What Python does without slots Without any declaration, each instance carries its own __dict__: class Point: def __init__(self, x: float, y: float) -> None: self.x = x self.y = y p = Point(1.0, 2.0) print(p.__dict__) # {'x': 1.0, 'y': 2.0} This dictionary allows adding attributes at runtime: ...