Outside the shared style. Position varies by use and must stay independent.

Flyweight separates intrinsic shared state from extrinsic per-use context. StyleFactory interns frozen Style objects by family and size. The pattern saves repeated representation, but does not bound the number of distinct configurations. Choose a lifetime or eviction policy when key cardinality can grow indefinitely.

What the function promises: Equal style keys return the same immutable object. Label data remains independently owned.

from dataclasses import dataclass

@dataclass(frozen=True)
class Style:
    family: str
    size: int

class StyleFactory:
    def __init__(self):
        self.styles = {}
    def get(self, family, size):
        if size <= 0:
            raise ValueError("Invalid size")
        key = family, size
        if key not in self.styles:
            self.styles[key] = Style(*key)
        return self.styles[key]

factory = StyleFactory()
a = {"x": 10, "style": factory.get("Sans", 14)}
b = {"x": 50, "style": factory.get("Sans", 14)}
assert a["style"] is b["style"]
assert a["x"] != b["x"]

Work and storage: Expected O(1) lookup, O(distinct styles) shared storage.

When to recognize it: A factory reuses a style for each key. If every style is unique, the factory can still grow without bound.

Check before applying it: Shared intrinsic data should not contain per-use mutable state.

No. Obtain another immutable style value and replace that label’s reference. Mutating shared state would affect every user of the same flyweight.