evolve_update.py

"""
Demo of TypedDict for payloads for a method on a dataclass that returns a new instance with updated attributes.
"""

from dataclasses import dataclass
from typing import TypedDict

class FooUpdate(TypedDict):
    prop_a: int
    prop_b: str
    prop_c: list[str]

@dataclass
class Foo:
    prop_a: int
    prop_b: str
    prop_c: list[str] 

    def evolve(self, update: FooUpdate):
        return self.__class__(
            prop_a = update.get('prop_a', self.prop_a),
            prop_b = update.get('prop_b', self.prop_b),
            prop_c = update.get('prop_c', self.prop_c)
            )

class FooChildUpdate(TypedDict):
    prop_a: int

class FooChild(Foo):

    def evolve(self, update: FooChildUpdate):
        return self.__class__(
            prop_a = update.get('prop_a', self.prop_a),
            prop_b = self.prop_b,
            prop_c = self.prop_c)


f = Foo(prop_a = 10, prop_b = 'str', prop_c = ['hi'])
f_evolved = f.evolve(update={'prop_a': 11})

fc = FooChild(prop_a=10, prop_b='str', prop_c = ['hi'])
fc_evolved = fc.evolve(update={'prop_a': 100})