Agent skill
fastapi-development
Build async APIs with FastAPI, including endpoints, dependency injection, validation, and testing. Use when creating REST APIs, web backends, or microservices.
Stars
232
Forks
15
Install this agent skill to your Project
npx add-skill https://github.com/aiskillstore/marketplace/tree/main/skills/bossjones/fastapi-development
SKILL.md
FastAPI Development
Quick start
Create a basic FastAPI application:
python
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
async def read_root():
return {"Hello": "World"}
@app.get("/items/{item_id}")
async def read_item(item_id: int, q: str | None = None):
return {"item_id": item_id, "q": q}
Run with:
bash
uv run uvicorn main:app --reload
Common patterns
Pydantic models for validation
python
from pydantic import BaseModel
from typing import Optional
class Item(BaseModel):
name: str
description: Optional[str] = None
price: float
tax: Optional[float] = None
@app.post("/items/")
async def create_item(item: Item):
return item
Dependency injection
python
from typing import Annotated
from fastapi import Depends
async def common_parameters(
q: str | None = None,
skip: int = 0,
limit: int = 100
):
return {"q": q, "skip": skip, "limit": limit}
CommonsDep = Annotated[dict, Depends(common_parameters)]
@app.get("/items/")
async def read_items(commons: CommonsDep):
return commons
Database dependencies with cleanup
python
async def get_db():
db = connect_to_database()
try:
yield db
finally:
db.close()
@app.get("/query/")
async def query_data(db: Annotated[dict, Depends(get_db)]):
return {"data": "query results"}
Error handling
python
from fastapi import HTTPException
@app.get("/items/{item_id}")
async def read_item(item_id: int):
if item_id < 1:
raise HTTPException(status_code=404, detail="Item not found")
return {"item_id": item_id}
Path and query validation
python
from typing import Annotated
from fastapi import Path, Query
@app.get("/items/{item_id}")
async def read_item(
item_id: Annotated[int, Path(gt=0, le=1000)],
q: Annotated[str, Query(max_length=50)] = None
):
return {"item_id": item_id, "q": q}
Response models
python
from pydantic import BaseModel
class ItemPublic(BaseModel):
id: int
name: str
price: float
@app.get("/items/{item_id}", response_model=ItemPublic)
async def read_item(item_id: int):
return ItemPublic(id=item_id, name="Laptop", price=999.99)
Testing with TestClient
python
from fastapi.testclient import TestClient
client = TestClient(app)
def test_read_root():
response = client.get("/")
assert response.status_code == 200
assert response.json() == {"Hello": "World"}
def test_read_item():
response = client.get("/items/42?q=test")
assert response.status_code == 200
assert response.json() == {"item_id": 42, "q": "test"}
Requirements
bash
uv add fastapi uvicorn
uv add "fastapi[all]" # Includes all optional dependencies
Key concepts
- Async/await: Use
async deffor I/O operations - Automatic validation: Request/response validation with Pydantic
- Dependency injection: Share logic across endpoints with
Depends - Type hints: Full editor support and validation
- Interactive docs: Auto-generated Swagger/OpenAPI at
/docs - Background tasks: Run tasks after response using
BackgroundTasks
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