CatenaConf

Introduction

CatenaConf is a lightweight Python library designed for managing and operating configurations. It extends the Python dictionary type to manage configurations using key-value pairs and provides flexible operation functionalities.

Features

• Lightweight: The code size is small and no third-party dependencies need to be installed (if you need to create a configuration from a Pydantic model or a yaml file, you need to install the corresponding dependencies).
• Dictionary based: Use Python dictionaries to create and manage configurations.
• Attribute access: Access and modify configuration values ​​through attributes, which is convenient and intuitive.
• Flexible update mechanism: Provides flexible update function and supports merging dictionaries.
• Reference resolution: Supports referencing other configuration values ​​in configuration values ​​and being able to resolve these references.

Installation

Install using pip:

pip install catenaconf

Usage

Creating Configuration

Create from dictionary

Catenaconf.create(config)

Description: Create a KvConfig instance (a built-in type of the library) from a dictionary.

Parameters:

• config (dict): A dictionary containing the configuration data.

Returns:

• Returns a KvConfig object created from the dictionary.

Usage:

from catenaconf import Catenaconf

config = {
    "database": {
        "host": "localhost",
        "port": 3306
    }
}

cfg = Catenaconf.create(config)

Load from file

Catenaconf.load(file)

Description: Load a KvConfig instance from a file. Supports JSON, YAML, and XML formats.

Parameters:

• file (str | pathlib.Path): Path to the configuration file.

Returns:

• Returns a KvConfig object created from the loaded data.

Usage:

cfg = Catenaconf.load("config.json")

Create from Pydantic Model

Catenaconf.structured(model)

Description: Creates a KvConfig instance from a Pydantic model.

Parameters:

• model (pydantic.BaseModel): A Pydantic model object to construct the configuration.

Returns:

• A KvConfig object containing the structured configuration.

Usage:

from pydantic import BaseModel

class MyModel(BaseModel):
    field: str
cfg = Catenaconf.structured(MyModel(field="value"))

Accessing Configuration

After creating a configuration, you can access configuration values using attribute access:

from catenaconf import Catenaconf

config = {
  "database": {
    "host": "localhost",
    "port": 3306
  }
}

cfg = Catenaconf.create(config)

# Accessing via attribute
host = cfg.database.host  
port = cfg.database.port

print(host)  # Output: localhost
print(port)  # Output: 3306

Selecting Configuration Values

Catenaconf.select(cfg, key, *, default="NOT FOUND", throw_on_resolution_failure=True, throw_on_missing=False)

Description: Selects a value from the configuration by key, with options for default values and error handling.

Parameters:

• cfg (KvConfig): The configuration instance to select from.
• key (str): The key to locate within the configuration.
• default (Any, optional): The default value to return if the key is not found. Defaults to "NOT FOUND".
• throw_on_resolution_failure (bool, optional): Whether to raise an error if key resolution fails. Defaults to True.
• throw_on_missing (bool, optional): Whether to raise an error for missing keys. Defaults to False.

Returns:

• The selected value, or the default value if the key is not found.

Usage:

value = Catenaconf.select(cfg, "database.user", default=None, throw_on_resolution_failure=False)

Updating Configuration

Catenaconf.update(cfg, key, value=None, *, merge=True)

Description: Updates the value of a specified key in the configuration.

Parameters:

• cfg (KvConfig): The configuration instance to update.
• key (str): The location of the value to be updated, specified as a dotted string.
• value (Any, optional): The new value to set.
• merge (bool, optional): Whether to merge dictionaries. Defaults to True.

Usage:

Catenaconf.update(cfg, "database.user", "root")
Catenaconf.update(cfg, "database", {"root": "root"})
Catenaconf.update(cfg, "database", {"root": "root"}, merge=True)

Notes:

• If merge=True, existing dictionaries are merged with the new value.

• If merge=False, the new value replaces the existing one.

Merging Configurations

Catenaconf.merge(*configs)

Description: Merges multiple configurations into one.

Parameters:

• *configs (KvConfig or dict): The configurations to merge, passed as positional arguments.

Returns:

• A merged KvConfig instance.

Usage:

config1 = {"database": {"host": "localhost"}}
config2 = {"database": {"port": 3306}}

merged_cfg = Catenaconf.merge(config1, config2)

References and Resolving References

Catenaconf.resolve(cfg)

Description: Resolve all references in the configuration. The reference is defined in the @{} format.

• @{a.b.c} : Reference keys in configuration. where a is the top-level key of the configuration, b is the sub-key of a, and c is the sub-key of b.

• @{a.b.1}: Reference elements in the list. where a is the top-level key of the configuration, b is the sub-key of a, and 1 is the index of b.

• @{env:VAR_NAME}: Reference environment variables.

Parameter:

• cfg (KvConfig): Contains the referenced configuration instance.

Usage:

config = {
    "config": {
        "database": {
            "host": "localhost",
            "port": 5432
        },
        "connection": "Host: @{config.database.host}, Port: @{config.database.port}"
    },
    "app":[
        "11", 
        "22",
        "33",
        "@{env:MY_VARIABLE}"    
    ],
    "list":[
        {"a": 1, "b": "@{app.1}"},
        {"ref": "@{config.database.host}"}
    ]
}

cfg = Catenaconf.create(config)
Catenaconf.resolve(cfg)

Notes:

• Resolves references by replacing placeholders with their actual values.

Converting to Dictionary

Catenaconf.to_container(cfg, resolve=True)

Description: Converts a KvConfig instance into a standard dictionary.

Parameters:

• cfg (KvConfig): The configuration instance to convert.
• resolve (bool, optional): Whether to resolve references in the dictionary. Defaults to True.

Returns:

• A standard dictionary containing the configuration data.

Usage:

dict_config = Catenaconf.to_container(cfg, resolve=True)
dict_config = Catenaconf.to_container(cfg, resolve=False)

Notes:

• When resolve=True, all references in the configuration are resolved.
• When resolve=False, references remain unresolved.