Skip to main content
StartPart 1BasicsPart 2Data StructuresPart 3Advanced PythonPart 4AI & ML

What is an API? REST Architecture Explained

Whenever you check live cricket scores, query weather forecasts, or ask ChatGPT a question in your Python app, you are talking to an API (Application Programming Interface).

An API is a messenger that allows two independent software programs to talk to each other over the internet.

1. The Real-World Metaphor: The Restaurant Waiter​

Think of a restaurant:

  • You (The Client / Python App): You sit at the table with the menu.
  • The Kitchen (The Server / Database): Where the food is prepared and stored.
  • The Waiter (The API): You give your food order (HTTP Request) to the waiter. The waiter walks to the kitchen, brings your food back, and delivers it to your table (HTTP Response).
+------------------+          HTTP Request (GET /weather)        +------------------+
|  Python Program  | ──────────────────────────────────────────> |   Cloud Server   |
|   (The Client)   | <────────────────────────────────────────── |   (Weather DB)   |
+------------------+          HTTP Response (JSON: 28°C)         +------------------+

2. Anatomy of an HTTP Request​

When your Python code talks to an API server, it sends four pieces of information:

  1. Endpoint (URL): Where the resource lives (e.g. https://api.github.com/users/octocat).
  2. HTTP Method (Action verb): What action you want the server to perform.
  3. Headers: Metadata (e.g. Content-Type: application/json or authentication tokens).
  4. Body (Payload): Data sent along with POST/PUT requests (e.g. login credentials).

3. The Core HTTP Action Verbs​

MethodWhat It DoesReal-World CRUD Equivalent
GETFetch data from the server (Read only)Read
POSTCreate a brand new resource on the serverCreate
PUT / PATCHUpdate or modify existing recordsUpdate
DELETERemove a record from the databaseDelete

4. Understanding HTTP Status Codes​

When an API answers back, it includes a 3-digit numerical status code indicating whether the request succeeded:

2xx: Success

• 200 OK: Request succeeded.
• 201 Created: New record saved.

3xx: Redirection

• 301 Moved Permanently: Resource has a new URL.

4xx: Client Mistakes

• 400 Bad Request: Invalid JSON syntax.
• 401 Unauthorized: Missing or invalid API key.
• 404 Not Found: Endpoint URL does not exist.

5xx: Server Crashes

• 500 Internal Server Error: Bug inside cloud server code.
• 503 Service Unavailable: Server overloaded.

Quick Summary​

  • REST API: Client-server communication protocol enabling programs to exchange JSON over HTTP/HTTPS.
  • HTTP Methods: GET (fetch data), POST (create new resource), PUT / PATCH (update), DELETE (remove).
  • Status Code Families: 2xx (Success), 3xx (Redirection), 4xx (Client Errors like 401 Unauthorized / 404 Not Found), 5xx (Server Errors).

What's Next?​

Let's learn how to make live HTTP GET requests, query parameters, and parse JSON using Python's requests library in Fetching Data with GET Requests!

Powered by Think IT Telugu