读取应用配置

前言

应用配置参数一般写在外部文件或环境变量中，大型系统可能还会写到专门的配置中心。FastAPI官方推荐通过环境变量的方式来读取配置参数，使用Pydantic直接解析出对应的配置参数信息。Pydantic还提供参数校验的功能。（PS: 当然，官方推荐归官方推荐，根据实际情况和个人喜好选择方案即可）

基于文件

配置文件多为*.ini、*.yaml、*.toml等格式的文件，这里以 yaml 文件为例

1. 安装读取yaml文件的依赖

python -m pip install pyyaml

2. yaml配置示例

database:
  mysql:
    host: "127.0.0.1"
    port: 3306
    user: "root"
    password: "123456"
    dbname: "test"
  redis:
    host: 
      - "192.168.0.10"
      - "192.168.0.11"
    port: 6379
    password: "123456"
    db: "5"

log:
  directory: "logs"
  level: "debug"
  maxsize: 100
  maxage: 30
  maxbackups: 30
  compress: true

3. 读取配置的代码

import yaml
import os

def read_yaml(filename: str = "conf/app.yaml"):
    if not os.path.exists(filename):
        raise FileNotFoundError(f"File {filename} not found")
    with open(filename, "r", encoding="utf-8") as f:
        config = yaml.safe_load(f.read())
        return config
    
if __name__ == "__main__":
    config = read_yaml("conf/app.yaml")
    print(type(config))
    print(config)

输出结果

<class 'dict'>
{'database': {'mysql': {'host': '127.0.0.1', 'port': 3306, 'user': 'root', 'password': '123456', 'dbname': 'test'}, 'redis': {'host': ['192.168.0.10', '192.168.0.11'], 'port': 6379, 'password': '123456', 'db': '5'}}, 'log': {'directory': 'logs', 'level': 'debug', 'maxsize': 100, 'maxage': 30, 'maxbackups': 30, 'compress': True}}

基于pydantic和.env环境变量

安装相关依赖

python3 -m pip install python-dotenv pydantic-settings

编辑 .env 文件

TITLE="My FastAPI App"
DESCRIPTION="This is a FastAPI app"
VERSION="0.0.1"
DEBUG=false

按照以前习惯，将配置相关功能放在pkg/config.py文件中

新版本pydantic已经将BaseSettings移到了pydantic-settings模块，旧版本还在pydantic。

from pydantic import validator
from pydantic_settings import BaseSettings

class Settings(BaseSettings):
    title: str
    description: str
    version: str
    debug: bool = False

    class Config:
        env_file = ".env"
        env_file_encoding = "utf-8"

    # 校验title字段必须有
    @validator("title",pre=True)
    def title_must_be_set(cls,v: str):
        if v is None:
            raise ValueError("title must be set")
        return v

settings = Settings()

编辑main.py文件，主要内容如下

from pkg.config import Settings
settings = Settings()

app = FastAPI(
    title=settings.title,
    description=settings.description,
    version=settings.version,
    docs_url=None,
    debug=settings.debug,
)