#5 CRUD Operations & In-Memory DB

Module 5 — CRUD Operations & In-Memory DB

In this module, you'll build full CRUD APIs (Create, Read, Update, Delete) using a simple in-memory database (Python dictionary). This is perfect for learning before connecting to SQL or NoSQL databases.

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1. Creating a Model & In-Memory DB

from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from uuid import uuid4

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float
    description: str | None = None

# In-memory database
db = {}

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2. CREATE (POST)

@app.post("/items")
async def create_item(item: Item):
    item_id = str(uuid4())
    db[item_id] = item
    return {"id": item_id, "item": item}

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3. READ ALL (GET)

@app.get("/items")
async def list_items():
    return db

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4. READ ONE (GET by ID)

@app.get("/items/{item_id}")
async def get_item(item_id: str):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    return db[item_id]

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5. UPDATE (PUT)

@app.put("/items/{item_id}")
async def update_item(item_id: str, item: Item):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    db[item_id] = item
    return {"id": item_id, "updated_item": item}

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6. DELETE (DELETE)

@app.delete("/items/{item_id}")
async def delete_item(item_id: str):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    del db[item_id]
    return {"deleted": item_id}

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7. Complete CRUD File (Copy-Paste Ready)

from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from uuid import uuid4

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float
    description: str | None = None

db = {}

@app.post("/items")
async def create_item(item: Item):
    item_id = str(uuid4())
    db[item_id] = item
    return {"id": item_id, "item": item}

@app.get("/items")
async def list_items():
    return db

@app.get("/items/{item_id}")
async def get_item(item_id: str):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    return db[item_id]

@app.put("/items/{item_id}")
async def update_item(item_id: str, item: Item):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    db[item_id] = item
    return {"id": item_id, "updated_item": item}

@app.delete("/items/{item_id}")
async def delete_item(item_id: str):
    if item_id not in db:
        raise HTTPException(status_code=404, detail="Item not found")
    del db[item_id]
    return {"deleted": item_id}

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