Architecture Patterns with Python

Whenever we have a business concept that has data but no identity, we often choose to represent it using the Value Object pattern. A value object is any domain object that is uniquely identified by the data it holds; we usually make them immutable: OrderLine is a value object @dataclass( frozen = True) class OrderLine: orderid: OrderReference sku: ProductReference qty: Quantity One of the nice things that dataclasses (or namedtuples) give us is value equality, which is the fancy way of saying, “Two lines with the same orderid, sku, and qty are equal.”