HTTP

What Is HTTP?

HTTP stands for HyperText Transfer Protocol.

It is a set of rules that defines how clients and servers communicate.

For example, when you open a website:

Your Browser
      ↓
HTTP Request
      ↓
Web Server
      ↓
HTTP Response
      ↓
Your Browser

The browser is the client, and the server is the computer that processes the request.

Client and Server

The two most important concepts are client and server.

Client

The client is the application that makes the request.

Examples:

• Web browser
• Python application
• Mobile application
• Frontend application

Server

The server receives the request, processes it, and sends a response.

Client
  │
  │ Request
  ↓
Server
  │
  │ Response
  ↓
Client

What Is an HTTP Request?

An HTTP request is a message sent from a client to a server asking the server to perform an action or return information.

For example:

GET /users

This can be understood as:

GET
 ↓
I want to retrieve data

/users
 ↓
I want the users resource

What Is an HTTP Response?

After receiving a request, the server sends an HTTP response.

A response normally contains a status code and may contain data.

HTTP/1.1 200 OK

{
    "name": "John",
    "age": 25
}

Here:

• 200 means the request succeeded.
• The JSON contains the requested data.

HTTP Methods

HTTP methods tell the server what type of operation the client wants to perform.

GET /products

POST /users

PUT /users/10

PATCH /users/10

DELETE /users/10

URL

A URL tells the client where the server resource is located.

https://example.com/products

The main parts are:

https://example.com/products
│       │           │
│       │           └── Resource
│       │
│       └── Domain
│
└── Protocol

When working with APIs, the URL usually points to an API endpoint.

https://api.example.com/products

What Is an API Endpoint?

An endpoint is a specific URL where an API provides a particular resource or operation.

For example:

GET /products
GET /products/10
GET /users
GET /orders

These can represent different API endpoints.

Think of an endpoint as a specific door into an API.

HTTP Status Codes

The server uses status codes to tell the client what happened to the request.

2xx — Success

200 OK
201 Created
204 No Content

The request was successfully processed.

4xx — Client Error

400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found
429 Too Many Requests

Something is wrong with the request or the client does not have permission to perform the operation.

5xx — Server Error

500 Internal Server Error
502 Bad Gateway
503 Service Unavailable

The server or an upstream service encountered a problem.

HTTP Request Using Python

Python can communicate with HTTP servers using libraries such as requests.

Install it with:

pip install requests

Then:

import requests

response = requests.get(
    "https://httpbin.org/get"
)

print(response.status_code)
print(response.text)

The important part is:

requests.get(...)

This sends an HTTP GET request to the server.

Understanding the Response

The response object contains information returned by the server.

import requests

response = requests.get(
    "https://httpbin.org/get"
)

print(response.status_code)
print(response.headers)
print(response.text)

Three useful properties are:

• status_code — HTTP status code
• headers — information about the response
• text — response body as text

HTTP and JSON

APIs commonly return data as JSON.

Python's Requests library can convert a JSON response into Python data using .json().

import requests

response = requests.get(
    "https://httpbin.org/json"
)

data = response.json()

print(data)

This is an important pattern that you will use throughout the rest of this course:

Python
  ↓
HTTP Request
  ↓
API
  ↓
HTTP Response
  ↓
JSON
  ↓
Python Dictionary / List

Real-World Example

Imagine a weather application.

The Python application wants today's weather.

Python Weather App
        │
        │ GET /weather
        ↓
Weather API
        │
        │ 200 OK
        │
        │ JSON
        ↓
Python Weather App
        │
        ↓
Display Weather

The same concept is used by AI applications.

Python AI Application
        │
        │ HTTP Request
        ↓
AI API
        │
        │ HTTP Response
        ↓
JSON Response
        │
        ↓
Python Application

HTTP vs API

These two concepts are related, but they are not the same thing.

GET
POST
PUT
PATCH
DELETE

GET /users
POST /users
GET /products
DELETE /orders/10

In simple terms:

HTTP
 ↓
Rules for communication

API
 ↓
Functionality exposed by an application

Complete Python Example

Here is a small example that brings the basic concepts together.

import requests


url = "https://httpbin.org/get"


response = requests.get(
    url,
    timeout=10
)


print("Status Code:")
print(response.status_code)


print("\nResponse Headers:")
print(response.headers)


print("\nResponse Data:")
print(response.json())

The process is:

1. Create URL
      ↓
2. Send GET request
      ↓
3. Server processes request
      ↓
4. Server sends response
      ↓
5. Check status code
      ↓
6. Read response data

What You Learned

• What HTTP is
• Client and server communication
• HTTP requests
• HTTP responses
• URLs and API endpoints
• GET, POST, PUT, PATCH and DELETE
• HTTP status codes
• Using HTTP from Python
• Reading JSON responses
• How HTTP is used by AI applications

Client
  ↓
HTTP Request
  ↓
API / Server
  ↓
HTTP Response
  ↓
JSON Data
  ↓
Python Application