Model design

Design the Post and Comment class skeleton.

Project: Blog app

In this five-lesson project you'll build a blog app. Each lesson adds one piece, and by the final lesson you'll complete a working mini command-line application.

You'll use what you learned in previous groups: classes, dataclasses and lists. Throughout the project you'll design a Post class that holds title, content and author. You'll add a Comment class and link comments to posts. Then a Blog class will let you add multiple posts and search through them.

Post and Comment skeleton

A post carries three core pieces of data: title, content and author. With the @dataclass decorator you define this class in a short form: each field name gets a type and an empty-string default.

A comment holds an author name and a short text. You define both classes separately; linking comments to posts is the next lesson. You'll also see field(default_factory=list) for an empty-list default.

Exercise Define the Post and Comment classes

Write the first piece of this project. Define a Post class with the @dataclass decorator; include fields title: str = "", content: str = "" and author: str = "". Define a Comment class the same way with author: str = "" and text: str = "". Then create a post with p = Post(title="First post", content="Hello", author="Ayşe") and print its title with print(p.title).

Show example solution

from dataclasses import dataclass, field

@dataclass
class Post:
    title: str = ""
    content: str = ""
    author: str = ""

@dataclass
class Comment:
    author: str = ""
    text: str = ""

p = Post(title="First post", content="Hello", author="Ayşe")
print(p.title)

Test yourself

Why write a blog app with classes?
- Post data and behavior stay in one unit; code is reusable.
- It can be written without classes, no difference.
- Classes only work in projects with a database.
- Using classes always slows the program down.
Show answer

Post data and behavior stay in one unit; code is reusable. — A class bundles post data and behavior in one unit, so you can reuse the code in other projects.

Complete the type of the Post field

@dataclass
class Post:
    title: ____ = ""
    content: str = ""
    author: str = ""

Show answer

@dataclass
class Post:
    title: str = ""
    content: str = ""
    author: str = ""

Match the blog project concepts

Post

Holds post data
Comment

Holds comment data
title

Post title
author

Post or comment writer

Next lesson: Blog class

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