kon 0.0.1

A configuration file(s) management library

Table of contents

• Overview

• Installation

• Usage

  • Basic Usage

    • Load Behavior

  • JSONFileHandler

    • Options

  • INIFileHandler

    • Options

    • Customizing SafeConfigParser

    • Implementation Details

Overview

kon is a very simple configuration file(s) management system that parses one or more configuration files in a path and provides an object tree that can be accessed directly. It also attempts to parse the data as concrete types so that you don’t have to explicitly get specific types, only for INI files. This does introduce some constraints and deviations from default implementations in python, but the convenience is generally worth it. Moreover this behavior can be overridden. kon currently handles only INI and JSON files.

Installation

Install the extension using pip:

$ pip install kon

or easy_install:

$ easy_install kon

Usage

Basic Usage

You can instantiate a Konfig object by calling its constructor:

from kon import Konfig

cfg = Konfig('/path/to/folder/or/ini-file')
# this can also accept options for loading by handlers
cfg.load()

The load method will try to get an appropriate file handler based on the filename extension. If none exists, it will skip that file. The file handlers are instantiated with any default values you may want to provide the configuration. For each file handler it then calls the instance’s load method. This method can accept handler specific loading options. Currently supported handlers and their behaviors are documented below.

If you want to specify default arguments, you can pass them in as keywords arguments to the constructor and they are passed through to the file handlers used to load the files.

from kon import Konfig

cfg = Konfig('/path/to/folder/or/ini-file', a=1, b=2.2, c=False)
cfg.load()

Load Behavior

The load method does a couple of things.

• It will walk the directory tree starting from the root directory you provide in the constructor call and create objects per directory as it goes along.

• Once it encounters a file, it will try to get a file handler for that type of file.

• If it cannot get a file handler, the file will be skipped.

• If it can get the file handler, it will instantiate it, pass it in the defaults it got and then call it’s load method passing in any parameters it got.

For e.g. if you have a directory tree like the following:

kon
├── a.ini
├── b
│   ├── c.ini
│   ├── d.json
│   ├── e
│   │   └── e.ini
│   ├── g.json
│   └── h.ini
├── i.ini
├── j.ini
└── k.ini

The corresponding object tree created by load before calling the handlers load will be exactly like the tree above sans the filename extension.

In the event that you have a folder and a file by the same prefix, for e.g.:

kon
├── a.ini
└── a.ini
    └── c.ini

it will result in a single object kon.a with merged sub-children.

JSONFileHandler

This handler parses JSON files that it finds in the path specified or an individual file if it is so specified. Internally it delegates to the default python json library.

Options

preserve_case

If set to false normalizes the key names to be lower case. By default the json loads function preserves case. This is the opposite of what happens with INIFileHandler.

encoding

Passthrough option for json.loads

INIFileHandler

This handler parses INI files that it finds in the path specified or an individual file if it is so specified. Internally it uses SafeConfigParser to load and parse the files. The individual sections, options and values are processed again.

Options

preserve_case

If set to true preserves the case of the option names. Sections are still case-insensitive. By default SafeConfigParser normalizes all option names to lower case. This will prevent that.

dict_type

Passthrough option for SafeConfigParser, see below

allow_no_value

Passthrough option for SafeConfigParser, see below

Customizing SafeConfigParser

If you want to customize the way the internal SafeConfigParser works you can use the arguments as specified in the RawConfigParser constructor documentation and pass them to the load method call on a Konfig instance.

Warning

Do not pass in the defaults argument as that will be ignored. The defaults that are sent to the parser should be provided as keyword arguments to the constructor.

For example:

cfg = Konfig('/path/to/folder/or/ini-file')
cfg.load(dict_type=OrderedDict, allow_no_value=True)

Implementation Details

Konfig uses SafeConfigParser to load the INI file. Consequently you get the built-in parsing and interpolation capabilities of the parser.

Because SafeConfigParser does not automatically coerce the values to an appropriate type, kon will try to do it’s best to do some for you. The following cast attempts are made in order of precedence:

• int

• float

• boolean

• list, dict or tuple (using ast.literal_eval)

Note

• The behavior deviates from SafeConfigParser’s treatment of boolean because a type-coercion to int happens before a type-coercion to boolean. So if you want a boolean set it to one of yes, no, on, off, true or false only.