FastAPI: FastAPI 简介 — 为什么它是下一代 Python Web 框架

from fastapi import FastAPI

app = FastAPI()

@app.get("/products/{product_id}")
async def get_product(product_id: int):
    # Type hint automatically validates & generates docs
    return {"product_id": product_id, "name": "Widget"}

import asyncio
import time

# WSGI style - blocks thread
def sync_handler():
    time.sleep(1)  # Thread blocked for 1 second
    return "done"

# ASGI style - non-blocking
async def async_handler():
    await asyncio.sleep(1)  # Event loop switches to other tasks
    return "done"

import asyncio
import time

async def fetch_price(product_id: int) -> dict:
    # Simulate database I/O latency
    await asyncio.sleep(0.1)
    return {"product_id": product_id, "price": 9.99}

async def main():
    start = time.perf_counter()
    # 100 concurrent requests - async finishes in ~0.1s
    results = await asyncio.gather(*[fetch_price(i) for i in range(100)])
    elapsed = time.perf_counter() - start
    print(f"Async: {len(results)} items in {elapsed:.2f}s")

asyncio.run(main())

执行成功

Async: 100 items in 0.10s

# === FastAPI: Type hints = auto validation + docs ===
from fastapi import FastAPI
from pydantic import BaseModel

class Product(BaseModel):
    name: str
    price: float

app = FastAPI()

@app.post("/products")
async def create_product(product: Product):
    return product  # Auto validated, auto documented

# 函数定义成功

# === Flask: Manual validation, no auto docs ===
from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route("/products", methods=["POST"])
def create_product():
    data = request.get_json()
    if not data or "name" not in data or "price" not in data:
        return jsonify({"error": "Invalid data"}), 400
    if not isinstance(data["price"], (int, float)):
        return jsonify({"error": "Price must be number"}), 400
    return jsonify(data)

from fastapi import FastAPI, Query
from typing import Optional

app = FastAPI()

@app.get("/prices")
async def search_prices(
    min_price: float = Query(0.0, ge=0, description="Minimum price in USD"),
    max_price: float = Query(999999.0, le=999999, description="Maximum price in USD"),
    category: Optional[str] = Query(None, max_length=50),
):
    return {"min_price": min_price, "max_price": max_price, "category": category}

# 函数定义成功

# After defining the endpoint above, visit:
# http://localhost:8000/docs  -> Swagger UI
# http://localhost:8000/redoc -> ReDoc
# http://localhost:8000/openapi.json -> Raw OpenAPI schema

{
  "paths": {
    "/prices": {
      "get": {
        "summary": "Search Prices",
        "parameters": [
          {"name": "min_price", "in": "query", "schema": {"type": "number", "minimum": 0.0}}
        ]
      }
    }
  }
}

from fastapi import FastAPI
from starlette.middleware.cors import CORSMiddleware
from starlette.responses import JSONResponse

app = FastAPI()

# Starlette middleware works seamlessly with FastAPI
app.add_middleware(CORSMiddleware, allow_origins=["*"])

# Starlette response classes work too
@app.get("/health")
async def health_check():
    return JSONResponse({"status": "healthy"})

# 函数定义成功

from fastapi import FastAPI
from pydantic import BaseModel, Field

class PriceCreate(BaseModel):
    product_id: int = Field(gt=0)
    price: float = Field(gt=0, description="Price in USD")
    currency: str = Field(default="USD", max_length=3)

app = FastAPI()

@app.post("/prices")
async def create_price(data: PriceCreate):
    # data is already validated & parsed by Pydantic
    validated = data.model_dump()
    return {"status": "created", "data": validated}

# 函数定义成功

from fastapi import FastAPI
from pydantic import BaseModel, Field
from typing import Optional

app = FastAPI(title="PriceTracker API", version="0.1.0")

class ProductCreate(BaseModel):
    name: str = Field(max_length=200)
    category: str = Field(max_length=100)
    base_price: float = Field(gt=0, description="Base price in USD")

class ProductResponse(BaseModel):
    id: int
    name: str
    category: str
    base_price: float

PRODUCTS_DB: dict[int, dict] = {}
_counter = 0

@app.post("/products", response_model=ProductResponse)
async def create_product(product: ProductCreate):
    global _counter
    _counter += 1
    record = {"id": _counter, **product.model_dump()}
    PRODUCTS_DB[_counter] = record
    return record

@app.get("/products/{product_id}", response_model=ProductResponse)
async def get_product(product_id: int):
    if product_id not in PRODUCTS_DB:
        from fastapi import HTTPException
        raise HTTPException(status_code=404, detail="Product not found")
    return PRODUCTS_DB[product_id]

# 函数定义成功

from fastapi import FastAPI
from pydantic import BaseModel, Field

app = FastAPI(title="PriceTracker Demo")

class PriceResponse(BaseModel):
    product_id: int = Field(gt=0)
    product_name: str
    price: float = Field(gt=0)
    currency: str = "USD"

PRICES_DB: dict[int, dict] = {
    1: {"product_id": 1, "product_name": "Widget", "price": 9.99},
    2: {"product_id": 2, "product_name": "Gadget", "price": 24.50},
}

@app.get("/products/{product_id}", response_model=PriceResponse)
async def get_price(product_id: int):
    if product_id not in PRICES_DB:
        from fastapi import HTTPException
        raise HTTPException(status_code=404, detail="Product not found")
    return PRICES_DB[product_id]

GET /products/1 → {"product_id":1,"product_name":"Widget","price":9.99,"currency":"USD"}
GET /products/99 → 404 Not Found