$ pip install etcaetera
$ git clone git@github.com:oleiade/etcaetera
$ cd etcaetera
$ python setup.py install
A real world example is worth a thousand words
>>> from etcaetera.config import Config
>>> from etcaetera.adapters import Defaults, Module, Overrides, Env, File
# Let's create a new configuration object
>>> config = Config()
# And create a bunch of adapters
>>> env_adapter = Env("MY_FIRST_SETTING", "MY_SECOND_SETTING")
>>> python_file_adapter = File('/etc/my/python/settings.py')
>>> json_file_adapter = File('/etc/my_json_settings.json')
>>> module_adapter = Module(os)
>>> overrides = Overrides({"MY_FIRST_SETTING": "my forced value"})
# Let's register them
>>> config.register(env_adapter, python_file_adapter, json_file_adapter, module_adapter, overrides)
# Load configuration
>>> config.load()
# And that's it
>>> print config
{
"MY_FIRST_SETTING": "my forced value",
"MY_SECOND_SETTING": "my second value",
"FIRST_YAML_SETTING": "first yaml setting value found in yaml settings",
"FIRST_JSON_SETTING": "first json setting value found in json settings",
...
}
The config object is the central place for your whole application settings. It loads your adapters in the order you’ve registered them, and updates itself using it’s data. Furthermore you can attach sub config objects to it, in order to keep a clean configuration hierarchy.
Please note that Defaults adapter will always be loaded first, and Overrides will always be loaded last.
>>> from etcaetera.config import Config
>>> from etcaetera.adapters import Defaults, Module, Overrides, Env, File
# Let's create a new configuration object
>>> config = Config()
# And create a bunch of adapters
>>> env_adapter = Env("MY_FIRST_SETTING", "MY_SECOND_SETTING")
>>> python_file_adapter = File('/etc/my/python/settings.py')
>>> json_file_adapter = File('/etc/my_json_settings.json')
>>> module_adapter = Module(os)
>>> overrides = Overrides({"MY_FIRST_SETTING": "my forced value"})
# Let's register them
>>> config.register(env_adapter, python_file_adapter, json_file_adapter, module_adapter, overrides)
# Load configuration
>>> config.load()
# And that's it
>>> print config
{
"MY_FIRST_SETTING": "my forced value",
"MY_SECOND_SETTING": "my second value",
"FIRST_YAML_SETTING": "first yaml setting value found in yaml settings",
"FIRST_JSON_SETTING": "first json setting value found in json settings",
...
}
# If you need a certain hierarchy for your configuration
# Config objects supports sub configs. Here's an example of
# how to add an "aws" subconfig
>>> aws_config = Config() # Create a config obj
>>> aws_env = Env("AWS_ACCESS_KEY_ID", "AWS_SECRET_ACCESS_KEY")
>>> aws_config.register(aws_env) # Register an env adapter on to it
>>> config.add_subconfig('aws', aws_config)
>>> config.aws
{
"AWS_ACCESS_KEY_ID": "128u09ijod019jhd182o1290d81",
"AWS_SECRET_ACCESS_KEY": "qoiejdn0182hern1d098uj12podij1029udaiwjJBIU09u0oimJHKI"
}
# Config objects are also able to automatically format the keys incoming
# from adapters. For example if you'd want all your keys to be lowercased
# just pass it the appropriate formatter (from etcaetera.formatters import *)
>>> from etcaetera.formatters import lowercased
>>> formatted_config = Config(formatter=lowercased)
>>> env_adapter = Env(**{"USER": "SUPER_DUPER_USER"})
>>> formatted_config.register(env_adapter)
>>> formatted_config.load()
>>> print formatted_config
{
"super_duper_user": "oleiade",
}
Adapters are the interfaces with configuration sources. They load settings from their custom source type, and they expose them as a normalized dict to Config objects.
Defaults adapter provides your configuration object with default values. It will always be evaluated first when Config.load method is called. You can whether provide defaults values to Config as a Defaults object or as a dictionary.
>>> from etcaetera.adapter import Defaults
# Defaults adapter provides default configuration settings
>>> defaults = Defaults({"ABC": "123"})
>>> config = Config(defaults)
>>> print config
{
"ABC": "123"
}
The Overrides adapter overrides Config object values with it’s own values. It will always be evaluated last when the Config.load method is called.
>>> from etcaetera.adapter import Overrides
# The Overrides adapter helps you set overriding configuration settings.
# When registered over a Config objects, it will always be evaluated last.
# Use it if you wish to force some config values.
>>> overrides_adapter = Overrides({"USER": "overrided value"})
>>> config = Config({
"USER": "default_value",
"FIRST_SETTING": "first setting value"
})
>>> config.register(overrides_default)
>>> config.load()
>>> print config
{
"USER": "overrided user",
"FIRST_SETTING": "first setting value"
}
Env adapter loads configuration variables values from system environment. You can whether provide it a list of keys to be fetched from environment. Or you can pass it a environment variables name to adapter destination name **mappings dict. Moreover, as adapters support nested keys through the . separator you can map any env var to a nested adapter destination.
>>> from etcaetera.adapter import Env
# You can provide keys to be fetched by the adapter at construction
# as keys
>>> env = Env("USER", "PATH")
>>> env.load()
>>> print env.data
{
"USER": "user extracted from environment",
"PATH": "path extracted from environment",
"PWD": "pwd extracted from environment"
}
# alternatively pass it as env var names to adapter var
# names dict
>>> os.environ["SOURCE"], os.environ["OTHER_SOURCE"]
("my first value", "my second value")
>>> env = Env({"SOURCE": "DEST", "OTHER_SOURCE": "TEST"})
>>> env.load()
>>> print env.data
{
"DEST": "my first value",
"TEST": "my second value"
}
# Adapters support nested destination too
>>> env = Env({"MY.USER": "USER"})
>>> env.load()
>>> print env.data
{
"MY": {
"USER": "oleiade",
}
}
The File adapter will load the configuration settings from a file. Supported formats are json, yaml and python module files. Every key-value pairs stored in the pointed file will be loaded in the Config object it is registered to.
The Python module files should be in the same format as the Django settings files. Only uppercased variables will be loaded. Any python data structures can be used.
Here’s an example
Given the following settings.py file
$ cat /my/settings.py
FIRST_SETTING = 123
SECOND_SETTING = "this is the second value"
THIRD_SETTING = {"easy as": "do re mi"}
ignored_value = "this will be ignore"
File adapter output will look like this:
>>> from etcaetera.adapter import File
>>> file = File('/my/settings.py')
>>> file.load()
>>> print file.data
{
"FIRST_SETTING": 123,
"SECOND_SETTING": "this is the second value",
"THIRD_SETTING": {"easy as": "do re mi"}
}
Given the following json file content:
$ cat /my/json/file.json
{
"FIRST_SETTING": "first json file extracted setting",
"SECOND_SETTING": "second json file extracted setting"
}
The File adapter output will look like this:
>>> from etcaetera.adapter import File
# The File adapter awaits on a file path at construction.
# All you have to do then, is to let the magic happen
>>> file = File('/my/json/file.json')
>>> file.load()
>>> print file.data
{
"FIRST_SETTING": "first json file extracted setting",
"SECOND_SETTING": "second json file extracted setting"
}
The Module adapter will load settings from a python module. It emulates the django settings module loading behavior, so that every uppercased locals of the module is matched.
Given a mymodule.settings module looking this:
MY_FIRST_SETTING = 123
MY_SECOND_SETTING = "abc"
Loaded module data will look like this:
>>> from etcaetera.adapter import Module
# It will extract all of the module's uppercased local variables
>>> module = Module(mymodule.settings)
>>> module.load()
>>> print module.data
{
MY_FIRST_SETTING = 123
MY_SECOND_SETTING = "abc"
}