Model design
- Python course
- Intermediate
- Lesson 59/116
- 6 min
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.
Practice 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).
Starter code
from dataclasses import dataclass, field
# Define the Post class: title, content, author fields
# Define the Comment class: author, text fields
# Create a Post instance and print its titleSample 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)Expected output
First post
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Why write a blog app with classes?
- Post data and behavior stay in one unit; code is reusable. Correct answer
- It can be written without classes, no difference.
- Classes only work in projects with a database.
- Using classes always slows the program down.
Explanation: A class bundles post data and behavior in one unit, so you can reuse the code in other projects.
2 Complete the type of the Post field
@dataclass
class Post:
title: ____ = ""
content: str = ""
author: str = ""@dataclass
class Post:
title: str = ""
content: str = ""
author: str = ""Explanation: The title field is text, so the type is str.
3 Match the blog project concepts
| Term | Meaning |
|---|---|
Post |
Holds post data |
Comment |
Holds comment data |
title |
Post title |
author |
Post or comment writer |