pip install pydantic

import pydantic
print(f"Pydantic版本：{pydantic.__version__}")

from pydantic import BaseModel
from typing import Optional

class User(BaseModel):
    name: str
    age: int
    email: str
    is_active: bool = True
    score: Optional[float] = None

# 正確數據
user1 = User(name="張三", age=25, email="zhangsan@example.com")
print(user1)

# age的數據類型與定義不一致，錯誤數據會拋出ValidationError
try:
    user2 = User(name="李四", age="二十五", email="invalid-email")
except Exception as e:
    print(f"驗證錯誤：{e}")

from pydantic import validator, Field

class Product(BaseModel):
    name: str = Field(..., min_length=1, max_length=50)
    price: float = Field(..., gt=0)
    category: str
    
    @validator('name')
    def name_must_contain_letters(cls, v):
        if not any(c.isalpha() for c in v):
            raise ValueError('名稱必須包含字母')
        return v.title()

class Address(BaseModel):
    street: str
    city: str
    zip_code: str

class Company(BaseModel):
    name: str
    address: Address
    employees: list[User]

class ConfigModel(BaseModel):
    class Config:
        # 允許額外字段
        extra = 'allow'
        # 字段別名
        allow_population_by_field_name = True
        # 驗證時是否轉換為對應類型
        validate_assignment = True

from fastapi import FastAPI
from typing import List

app = FastAPI()

class Item(BaseModel):
    name: str
    description: str = None
    price: float
    tags: List[str] = []

@app.post("/items/")
async def create_item(item: Item):
    return {"item": item.dict()}

import os
from pydantic import BaseSettings

class Settings(BaseSettings):
    app_name: str = "My App"
    database_url: str
    debug: bool = False
    
    class Config:
        env_file = ".env"

settings = Settings()

from pydantic import ValidationError

def validate_user_data(data: dict):
    try:
        user = User(**data)
        return user
    except ValidationError as e:
        print(f"驗證錯誤詳情：{e.json()}")
        return None

from typing import ForwardRef

class Department(BaseModel):
    name: str
    manager: 'User'  # 前向引用

class User(BaseModel):
    name: str
    department: Department

# 更新前向引用
User.update_forward_refs()

from pydantic import errors

class CustomUser(BaseModel):
    age: int
    
    @validator('age')
    def validate_age(cls, v):
        if v < 0:
            raise ValueError('年齡不能為負數')
        return v