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Optimizing Classes with `__slots__`

OOP Modern Tools

Using __slots__

`__slots__` tells Python to allocate a fixed set of attributes, eliminating the per-instance `__dict__`.

Define slotsKnow trade-offs

Definition​

class LightPoint:
    __slots__ = ("x", "y", "z")

    def __init__(self, x: float, y: float, z: float):
        self.x = x
        self.y = y
        self.z = z
  • Prevents creation of new attributes outside __slots__.
  • Reduces memory footprint and speeds attribute lookup.

Trade-offs​

  • Incompatible with __dict__ by default; add '__dict__' if you need dynamic attrs.
  • Doesn't play nicely with multiple inheritance unless all parents define slots.
  • Use when instantiating thousands of lightweight objects or running in tight loops.

Next up in your learning path

Dataclasses + slots

Set `slots=True` for dataclass convenience + performance.

Modern

Inheritance review

Plan slot usage with multi-level hierarchies.

Architecture

MRO deep dive

Understand lookup order for slot-based classes.

Internals