Week 1

Week 1

Join the github classroom assignment with the following link: https://classroom.github.com/a/KOc7f0j5

Once you join your repository will be created https://github.com/blueprint-learn/week1-techteam-sp26-{github-username}

You will get an email with access to your repo

Clone your repo

git clone https://github.com/blueprint-learn/week1-techteam-sp26-{github-username}.git

Goal for today

By the end of this class, you will understand what an API is and you will have written and run a real backend service.

Set expectations

This is not web dev with HTML

This is backend infrastructure

What we build today looks simple, but it’s the same pattern used by Netflix, Stripe, AWS, etc.

1. What Is an API?

Core idea

API = contract between a client and a server

You ask for data → server responds with data

Client (browser / app / script)

 |

 | HTTP request

 v

 API Server

 |

 | JSON response

 v

 Client

Key clarification

APIs don’t care who the client is

Browser, mobile app, another server — all the same

Examples

Instagram feed

Spotify playlists

Google Maps directions

2. REST & HTTP Basics

REST (high-level)

Everything is a resource

Each resource has a URL

HTTP Methods

Method

Meaning

GET

Read data

POST

Create data

PUT

Update data

DELETE

Remove data

HTTP Response

Status code (200, 404, etc.)

Body (usually JSON)

{

 "id": 3,

 "name": "Notebook",

 "price": 5.99

}

Important

JSON ≠ Python dictionary (but very similar)

3. Live Demo Setup

pip3 install -r requirements.txt

Minimal app

from fastapi import FastAPI

app = FastAPI()

@app.get("/")

def root():

 return {"message": "Hello World"}

Run the app

uvicorn app.main:app --reload

4. Endpoints & Path Parameters

@app.get("/items/{item_id}")

def read_item(item_id: int):

 return {"item_id": item_id}

Automatic validation

Type validation