一文带你搞懂Python FastAPI中所有核心参数的设置

from fastapi import FastAPI
app = FastAPI()

@app.get("/items/")
async def read_items(skip: int = 0, limit: int = 10):
    # `skip`和`limit`就是查询参数，如：/items/?skip=20&limit=5
    return {"skip": skip, "limit": limit}

@app.get("/items/{item_id}")
async def read_item(item_id: int):  # item_id 是路径参数
    return {"item_id": item_id}

from fastapi import Body

@app.put("/items/{item_id}")
async def update_item(
    item_id: int,
    name: str = Body(...),  # Body(...) 表示必需项
    description: str = Body(None)  # Body(None) 表示可选项
):
    return {"item_id": item_id, "name": name, "description": description}

from fastapi import Form

@app.post("/login/")
async def login(username: str = Form(...), password: str = Form(...)):
    return {"username": username}

from fastapi import Path, Query, Body

@app.put("/mixed-items/{item_id}")
async def update_mixed_item(
    *,
    item_id: int = Path(..., title="商品ID", ge=1),  # 路径参数，>=1
    q: str = Query(None, alias="query-string"),      # 可选查询参数，别名
    item: dict = Body(...)                           # 必需的JSON请求体
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})
    results.update({"item": item})
    return results

from pydantic import BaseModel, EmailStr
from typing import Optional, List

class UserCreate(BaseModel):
    # 必需字段
    username: str
    email: EmailStr  # 内置邮箱格式验证
    # 可选字段，带默认值
    full_name: Optional[str] = None
    # 列表类型
    tags: List[str] = []

@app.post("/users/")
async def create_user(user: UserCreate):  # 一个参数接管整个请求体
    # 直接访问已验证好的数据
    if user.full_name:
        greeting = f"Hello, {user.full_name}!"
    else:
        greeting = f"Hello, {user.username}!"
    return {"message": greeting, "user_info": user.dict()}

from fastapi import FastAPI, Path, Query, Body
from pydantic import BaseModel
from typing import Optional
from datetime import datetime

app = FastAPI(title="参数详解示例")

class Item(BaseModel):
    name: str
    description: Optional[str] = None
    price: float = Body(..., gt=0)
    tax: Optional[float] = None
    tags: list = []

@app.post("/advanced-items/{category}")
async def create_advanced_item(
    category: str = Path(..., description="物品分类"),
    item_id: int = Query(..., ge=1, description="物品ID"),
    q: Optional[str] = Query(None, max_length=50),
    urgent: bool = Query(False),
    item: Item = Body(..., example={  # 为文档提供示例
        "name": "Foo",
        "price": 50.5,
        "tags": ["cool", "new"]
    })
):
    """创建新物品的复杂端点"""
    total = item.price + (item.tax if item.tax else 0)
    result = {
        "category": category,
        "item_id": item_id,
        "query_string": q,
        "urgent": urgent,
        "item_name": item.name,
        "total_price": total,
        "created_at": datetime.now().isoformat()
    }
    return result

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)