Fast Api : Python Backend Framework

mkdir fastapi-backend

cd fastapi-backend

Create virtual environment (THIS IS IMPORTANT)

python3 -m venv venv

Activate it:

source venv/bin/activate

You should see:

(venv) wajahat@ubuntu:...

Install FastAPI + Uvicorn

pip install fastapi uvicorn

Create main.py

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def root():
    return {"message": "Hello FastAPI"}

Run the server

uvicorn main:app --reload

Open browser:

http://127.0.0.1:8000

Docs:

http://127.0.0.1:8000/docs

uv add python-dotenv

pip equivalent:

pip install python-dotenv

What it does:
This library loads environment variables from a .env file. Useful for secrets like API keys or database URLs without hardcoding them in your code.

uv add fastapi-users[sqlalchemy]

pip equivalent:

pip install "fastapi-users[sqlalchemy]"

What it does:
FastAPI Users is a user authentication and management library. The [sqlalchemy] extra installs support for SQLAlchemy databases, so you can easily handle signup, login, and user models.

uv add imagekitio

pip equivalent:

pip install imagekitio

What it does:
ImageKit.io is an SDK to work with the ImageKit service. It helps you upload, optimize, and manage images in your backend without writing custom image processing code.

uv add uvicorn[standard]

pip equivalent:

pip install "uvicorn[standard]"

What it does:
Uvicorn is the ASGI server that runs your FastAPI app. The [standard] extra adds recommended packages like httptools and uvloop for better performance.

uv add aiosqlite

pip equivalent:

pip install aiosqlite

What it does:
Aiosqlite is an async wrapper for SQLite. It lets your FastAPI app talk to a SQLite database using async/await, keeping your server fast and non-blocking.

Now you can add .env file and remember to
Project structure for scalability
As projects grow, it’s better to separate files:

project-root/
 ├── app/
 │   ├── main.py         # FastAPI app
 │   ├── models.py       # DB models
 │   ├── routes.py       # API endpoints
 │   └── config.py       # Settings, env loader
 ├── env/                # virtual environment
 ├── requirements.txt
 └── .env                # your secret keys

do this as projects grows…
peace out for now :)

from fastapi import FastAPI

app = FastAPI()

@app.get("/auth") # This is called a decorator in Python. Takes a function and modifies or registers it in some way.

def authenticating():

return {"isLoggedIn" : "saeed here "}

This is called a decorator in Python.

A decorator is something that:

Takes a function and modifies or registers it in some way.

@app.get("/auth")

“Whenever someone sends a GET request to /auth, run the function written below.”

Python internally converts this:

@app.get(“/auth”)

def authentication():

return {“hi” : “ I am saeed”}

into something like this:

def authenticating():

return {"isLoggedIn": "saeed here"}

app.get("/auth")(authenticating)

So basically:

• app.get("/auth") returns a function

• That function takes authenticating as argument

• FastAPI stores it in a routing table

So FastAPI now knows:

Route: GET /auth  →  Call authenticating()

@app.get("/user/{user_id}")

def get_user(user_id: int):

return {"user_id": user_id}

If you open:

/user/10

FastAPI automatically:

Extracts 10

Converts to int

Passes it into get_user()

This is called:

Path Parameter

run this command to run you app :

uvicorn app.app:app –reload