Introduction to REST

REST (Representational State Transfer) is a set of conventions for designing web APIs.

Core idea: resources

A REST API is organized around resources:

• /users
• /posts
• /orders

You use HTTP methods to operate on them:

• GET /users → list users
• GET /users/1 → get one user
• POST /users → create user
• PUT/PATCH /users/1 → update
• DELETE /users/1 → delete

Status codes matter

• 200 OK — success
• 201 Created — created successfully
• 400 Bad Request — invalid request data
• 401 Unauthorized — missing/invalid auth
• 403 Forbidden — authenticated but not allowed
• 404 Not Found — resource doesn’t exist

Statelessness

REST APIs are typically stateless:

• every request contains everything needed (auth token, parameters)

That’s why token-based auth (JWT) is common.

A good REST mental model

diagram Diagram mermaid

  flowchart LR
  Client -->|HTTP + JSON| API[Flask API]
  API -->|ORM| DB["(Database)"]
  DB --> API
  API -->|JSON + status| Client

Practical tip

REST is a guideline, not a law.

Aim for:

• consistency
• clear error responses
• predictable URLs

Visualize it

Here’s how the standard HTTP methods map onto CRUD operations for a single resource.

diagram HTTP methods as CRUD mermaid

  flowchart LR
  GET["GET"] --> Read["Read"]
  POST["POST"] --> Create["Create"]
  PUT["PUT/PATCH"] --> Update["Update"]
  DELETE["DELETE"] --> Delete["Delete"]
  Read --> R["/api/tasks"]
  Create --> R
  Update --> R
  Delete --> R

GET, POST, PUT/PATCH, and DELETE map to read, create, update, and delete on a resource such as /api/tasks

🧪 Try It Yourself

Exercise 1 – Create a Flask App

pch.exerciseTag pch.exerciseTitle

Exercise 2 – Dynamic Route

pch.exerciseTag pch.exerciseTitle

Exercise 3 – Return JSON

pch.exerciseTag pch.exerciseTitle