Immutable DTOs in Python

This example demonstrates how to create an immutable Data Transfer Object (DTO) in Python using dataclasses and how to define an Enum for status values.

Enum in Python

Python's enum module allows for the creation of enumerations, providing a way to define a set of named constants.

from enum import Enum

class Status(Enum):  # Enum equivalent to C# Status type
    ACTIVE = "Active"
    INACTIVE = "Inactive"
    GRADUATED = "Graduated"

Immutable DTO

The dataclasses module provides decorators and functions for automatically adding special methods such as __init__() and __repr__() to user-defined classes. By setting frozen=True, instances of the dataclass become immutable after creation.

from dataclasses import dataclass
# Assuming Status enum is in src.core.status
from src.core.status import Status

@dataclass(frozen=True)
class Student:
    id: int
    first_name: str
    last_name: str
    grade_point: float
    status: Status

# Example Usage:
# student1 = Student(id=1, first_name="Jane", last_name="Doe",
#                    grade_point=3.8, status=Status.ACTIVE)
# student1.first_name = "Janet"  # This would raise FrozenInstanceError