# 正确示例：显式类型注解
import os

from pydantic import BaseModel

class User(BaseModel):
    id: int  # 显式指定int类型
    name: str  # 显式指定str类型
    is_active: bool = True  # 带默认值的类型注解

# 错误示例：缺少类型注解
# class BadUser(BaseModel):
#     id = 1  # 缺少类型注解，Pydantic 2.9+将报错
#     name = "John"  # 缺少类型注解，Pydantic 2.9+将报错

os.environ['app_port'] = '8888'

# 环境变量自动映射示例
from pydantic_settings import BaseSettings, SettingsConfigDict


class AppConfig(BaseSettings):
    host: str = "localhost"
    port: int = 8000

    model_config = SettingsConfigDict(
        env_prefix="APP_",  # 环境变量前缀
        case_sensitive=False  # 不区分大小写
    )


# 当环境变量存在APP_PORT=8080时
config = AppConfig()
print(config.port)  # 输出: 8080 (而非默认的8000)