Defconf

Python Library/tool to easily define and validate the format and content of a configuration file

To build a robust application, it takes a lot of effort to properly check and validate everything that can goes wrong within an input file filled by users:

• Wrong option name : login VS username,
• Wrong type : string instead of integer,
• Mandatory information missing
• Value not conform (ip address not valid etc ..)

All this complexity is often not completely managed by the application has it require a LOT of work: Defconf is here to help, it will:

• Validate the format of the configuration file (list, dict, string)
• Validate all names and track unsupported options
• Validate content type (integer, string, bool, list, dict)
• Validate the value with REGEX or pre-define list
• Populate default value if information is missing

How does it work

Create a definition file to define how your configuration should look like

For this simple configuration file

http_server: [ 192.168.0.1, 192.168.0.2 ]
password: pwd!!
port: 4444

A corresponding defconf file will looks like this

validate:
  main:
    http_server: { type: list, validate: ip_addr, mandatory: 1 }
    password:    { type: string, validate: valid_password, mandatory: 1 }
    port:        { type: integer, values: [4444, 2580], default: 4444 }

regex:
  ip_addr: ^(\d+)\.(\d+)\.(\d+)\.(\d+)$
  valid_password: ^[A-Za-z0-9\!]+$

For each option on the configuration file, we can define:

• type => [string, integer, bool, dict, list]
• mandatory => [0, 1]
• values => List of supported values (only for integer, string and list type)
• validate => Advance validation with Regex or with another validate block (nested dict)
• default => Default value if option is not defined

Detail example available here :

• Configuration file - myconfig.yml
• Definition file - myconfig.def.yml

From CLI (within project folder)

python defconf.py myconfig.yml myconfig.def.yml

From python

import defconf

definition = yaml.load( open('myconfig.def.yml') )
config = yaml.load( open('myconfig.yml') )
defconf.validate_config( config, definition, 'myconfig' )

Installation

git clone https://github.com/dgarros/defconf

Enhancements list

• Support JSON file in addition to YAML
• Improve exception handling to catch as many issue as possible in one shot
• Create example config file from Definition file
• Create definition file for definition files :)
• Create a module and publish

Support

Bug and issues can be open on Github [https://github.com/dgarros/defconf/issues]

How to contribute

• Use it and share your config/def files
• Report issue
• Add unit tests
• Improve documentation