Pydantic Cheatsheet 09 — pydantic-settings

uv add pydantic-settings

from pydantic_settings import BaseSettings, SettingsConfigDict

class Settings(BaseSettings):
    database_url: str
    secret_key: str
    log_level: str = "INFO"
    
    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        env_prefix="MYAPP_",
        case_sensitive=False,
    )

settings = Settings()

# .env (don't commit)
MYAPP_DATABASE_URL=postgresql://...
MYAPP_SECRET_KEY=...
MYAPP_LOG_LEVEL=DEBUG

class DBSettings(BaseSettings):
    url: str
    pool_size: int = 10
    
    model_config = SettingsConfigDict(env_prefix="MYAPP_DB_")

class Settings(BaseSettings):
    db: DBSettings = DBSettings()
    secret_key: str
    
    model_config = SettingsConfigDict(env_prefix="MYAPP_")

MYAPP_DB_URL=postgresql://...
MYAPP_DB_POOL_SIZE=20
MYAPP_SECRET_KEY=...

class Settings(BaseSettings):
    db: DBSettings
    
    model_config = SettingsConfigDict(env_nested_delimiter="__")

MYAPP_DB__URL=postgresql://...

class Settings(BaseSettings):
    secret_key: str
    
    model_config = SettingsConfigDict(secrets_dir="/run/secrets")

model_config = SettingsConfigDict(env_file=(".env", ".env.local"))

from pydantic import SecretStr

class Settings(BaseSettings):
    api_key: SecretStr
    db_password: SecretStr

print(settings.api_key)                       # SecretStr('**********')
print(settings.api_key.get_secret_value())    # actual value

class Settings(BaseSettings):
    database_url: str
    debug: bool = False
    
    model_config = SettingsConfigDict(cli_parse_args=True)

# python myapp.py --database-url=... --debug

from pydantic_settings import BaseSettings, TomlConfigSettingsSource

class Settings(BaseSettings):
    model_config = SettingsConfigDict(toml_file="config.toml")
    
    @classmethod
    def settings_customise_sources(cls, settings_cls, *args):
        return (TomlConfigSettingsSource(settings_cls),) + args

from functools import lru_cache
from fastapi import Depends

@lru_cache
def get_settings() -> Settings:
    return Settings()

@app.get("/info")
async def info(s: Settings = Depends(get_settings)):
    return {"db": s.database_url[:20] + "..."}

class Settings(BaseSettings):
    env: Literal["dev", "staging", "prod"] = "dev"
    database_url: str
    
    @model_validator(mode="after")
    def prod_safety(self):
        if self.env == "prod" and "localhost" in self.database_url:
            raise ValueError("prod can't use localhost DB")
        return self

try:
    settings = Settings()
except ValidationError as e:
    print(e)
    sys.exit(1)

class Settings(BaseSettings):
    model_config = SettingsConfigDict(frozen=True)