Simplify Data Models with Python's `dataclasses` Module

from dataclasses import dataclass, field

# Define a simple data class for a User
@dataclass
class User:
    id: int
    name: str
    email: str = "[email protected]" # Default value

# Define a data class with a mutable default and post-init processing
@dataclass
class BlogPost:
    id: int
    title: str
    author: User
    tags: list[str] = field(default_factory=list) # Mutable default handled correctly
    created_at: str = field(init=False, repr=False) # Exclude from init and repr

    def __post_init__(self):
        # Perform any setup or validation after __init__
        import datetime
        self.created_at = datetime.datetime.now().isoformat()

# Create instances
user1 = User(1, "Alice")
user2 = User(2, "Bob", "[email protected]")
post1 = BlogPost(101, "Intro to Dataclasses", user1, ['python', 'webdev'])

# Dataclasses provide __repr__, __eq__ automatically
print(f"User 1: {user1}")
print(f"User 2: {user2}")
print(f"Post 1: {post1}")
print(f"Are user1 and a new user with same id/name equal? {user1 == User(1, 'Alice')}")

# Access fields
print(f"Post 1 title: {post1.title}, Author email: {post1.author.email}")
print(f"Post 1 created at (not in repr): {post1.created_at}")

# demonstrate mutable default
post2 = BlogPost(102, "Another Post", user2)
post2.tags.append('new tag')
print(f"Post 1 tags: {post1.tags}") # Original list not affected
print(f"Post 2 tags: {post2.tags}") # New list for post2