Getting Started

essex-config is a Python library for creating configuration objects that read from various sources, including files, environment variables, and Azure Key Vault.

pip install essex-config

Basic Usage

Create a configuration object for connecting to a customer database:

from pydantic import BaseModel, Field
from essex_config import load_config

class CustomerDatabase(BaseModel):
    """Configuration for connecting to the Customer Database"""
    host: str = Field(default="127.0.0.1", description="DB connection host")
    port: int = Field(description="DB connection port")
    password: str = Field(description="DB connection password")

if __name__ == "__main__":
    config = load_config(CustomerDatabase)
    print(config)

When load_config(CustomerDatabase) is executed, values are populated from environment variables or default values.

Nested Configurations

Nest configuration objects:

class Inner(BaseModel):
    inner_hello: str

class NestedConfiguration(BaseModel):
    hello: str
    nested: Inner

nested_config = load_config(NestedConfiguration)

load_config() populates every field, including nested_config.nested.inner_hello. The default prefix for every field in Inner is nested, which can be changed with Annotated[Inner, Prefixed("new_prefix")].

String Interpolation

Environment Variables

For configuration files, environment variables are used to fill string templates. For example, if your config contains ${TEST_VALUE}, the value is fetched from the TEST_VALUE environment variable. This also supports lists and dictionaries, such as ["${TEST_VALUE}", "world"] and {"key": "${TEST_VALUE}", "key2": "world"}.

Self Configuration Reference

Self-reference works by replacing values from the same configuration source it is reading. For example, if your config contains:

{
    "host": "localhost",
    "port": 8080,
    "url": "http://${self.host}:${self.port}"
}

The url gets populated with the host and port defined in the source.