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Why? I thought one should prefer immutability. As for typed dicts.. yes, I’m mostly stuck on old python versions, nice reminder.
by ansgri 2y ago
Why? I thought one should prefer immutability. As for typed dicts.. yes, I’m mostly stuck on old python versions, nice reminder.
- maleldil 2y agoYou can use TypedDict from `typing_extensions` if your version doesn't have it. You can use a lot of the newer stuff from there, too, especially if you enable `__future__.annotations`. How old is your Python, though? TypedDict is from 3.8. That was 5 years ago.
- throwaway2037 2y agoYou can use: > @dataclass(frozen=True) to create an immutable data class.
- maleldil 2y agoWhile that works (and I use it extensively), it's a bit hacky. You have to use `object.__setattr__` to set attributes in `__init__` or `__post_init__`, which looks so wrong.
- maxbond 2y agoI think the cleaner alternative would be to use a static or class method as an alternative constructor and use the init the dataclass decorator provides for you. Eg something like: @dataclass(frozen=True) class Foo: bar: int baz: str @classmethod def new(cls, bar: int) -> "Foo": baz = calculate_baz(bar) return cls(bar, baz) foo = Foo.new(10)
- throwaway2037 2y agoWhat is wrong with a static factory method?
- int_19h 2y agoIn general, preferring immutability is great. In Python specifically, it can be hard to pull off given that e.g. something as basic as dict does not have a standard immutable equivalent. You inevitably have to rely on conventions - basically saying "this is supposed to be immutable" rather than enforcing it.