Immutability

Update Immutable Records with Python copy.replace()

I like immutable value objects because they make state changes explicit. The awkward part is that Python has historically offered several different ways to create a slightly modified version of one. A dataclass has dataclasses.replace(). A named tuple has _replace(). A custom class usually needs its own helper. The operations are conceptually similar, but generic code has no single interface to target. Python 3.13 adds copy.replace() to close that gap. It creates a new object of the same type while replacing selected fields, and it works with dataclasses, named tuples, and classes that implement __replace__().