Build a REST API with FastAPI and SQLite

From zero to a documented, validated CRUD API in one file. FastAPI is the fastest way to ship a Python back end.

Web & Backend2026-08-089 min readFastAPI · SQLite · REST

In this guide

  1. Install and model your data
  2. Read (with validation for free)
  3. Create and update
  4. Run it and see the docs

FastAPI gives you automatic request validation, serialisation and interactive docs — for free, from type hints alone. Paired with SQLite you have a real, deployable API in one file.

Install and model your data

bash
pip install "fastapi[standard]" sqlmodel
python
from typing import Optional
from sqlmodel import SQLModel, Field, create_engine, Session, select
from fastapi import FastAPI, HTTPException

class Item(SQLModel, table=True):
    id: Optional[int] = Field(default=None, primary_key=True)
    name: str
    price: float
    in_stock: bool = True

engine = create_engine("sqlite:///inventory.db")
SQLModel.metadata.create_all(engine)

app = FastAPI(title="Inventory API")

Read (with validation for free)

python
@app.get("/items")
def list_items():
    with Session(engine) as s:
        return s.exec(select(Item)).all()

@app.get("/items/{item_id}")
def get_item(item_id: int):
    with Session(engine) as s:
        item = s.get(Item, item_id)
        if not item:
            raise HTTPException(404, "item not found")
        return item

Create and update

python
@app.post("/items", status_code=201)
def create_item(item: Item):
    with Session(engine) as s:
        s.add(item)
        s.commit()
        s.refresh(item)
        return item

@app.patch("/items/{item_id}")
def update_item(item_id: int, patch: Item):
    with Session(engine) as s:
        item = s.get(Item, item_id)
        if not item:
            raise HTTPException(404, "item not found")
        for k, v in patch.model_dump(exclude_unset=True).items():
            setattr(item, k, v)
        s.add(item); s.commit(); s.refresh(item)
        return item

Run it and see the docs

bash
uvicorn main:app --reload
# open http://localhost:8000/docs  → interactive Swagger UI
Those docs aren't just for show — every endpoint is callable right from the browser. It's the fastest feedback loop in web development.

Swap SQLite for Postgres by changing one connection string when you grow. That's the whole migration story — FastAPI is that clean.

Keep reading

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