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derpconf

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derpconf abstracts loading configuration files for your app. derpconf was extracted from thumbor.

Intalling

Installing derpconf is as easy as:

pip install derpconf

Usage

Using it is as simple as:

from derpconf.config import Config

conf = Config.load('/path/to/my/cfg.conf')

assert conf.MY_KEY == 'MY_VALUE' # assuming there's a key called MY_KEY in
                                 # the configuration file.

Settings Defaults

If you want to set default values for your configurations, just call:

Config.define('MY-KEY', 'DEFAULT VALUE', 'Description for my key', 'Section')

The values that define gets are:

  • the configuration key;
  • the default value for that key if it's not found in the configuration file;
  • the description for this key. This is very useful for generating configuration file examples.
  • the section that this key belongs to. Again very useful for generating configuration file examples.

Using Environment Variables

If you wish to allow environment variables to be used as the value of configuration keys, just call the allow_environment_variables method in your config.py file:

from derpconf.config import Config

Config.allow_environment_variables()

If there's an environment variable with the same name as the given configuration, derpconf will give precedence to it, instead of using the default value or the value in the configuration file.

# called program with SOMETHING=value myprogram.py
assert config.SOMETHING == "value"

# even if the default for 'SOMETHING' or the value in the config file is different from 'value'

Reloading Configurations

After you've loaded configurations from a file, sometimes it's needed to have them reloaded. This is the case when a new module needs to define some new default values.

In order to reload values from a config object, just call reload on it:

from derpconf.config import Config

conf = Config.load('/path/to/my/cfg.conf')

# then later on...

Config.define('SOMENEWFOO', 'bar', 'baz', 'foo')

conf.reload()
assert conf.SOMENEWFOO == 'bar'

Generating Configuration Examples

To generate a configuration example, you just need to call the get_config_text method. Let's see an example:

from derpconf.config import Config

Config.define('foo', 'fooval', 'Foo is always a foo', 'FooValues')
Config.define('bar', 'barval', 'Bar is not always a bar', 'BarValues')
Config.define('baz', 'bazval', 'Baz is never a bar', 'BarValues')

config_sample = Config.get_config_text()
print config_sample # or instead of both, just call generate_config()

The following text will be print into the standard output:

################################## FooValues ###################################

## Foo is always a foo
## Defaults to: fooval
#foo = 'fooval'

################################################################################


################################## BarValues ###################################

## Bar is not always a bar
## Defaults to: barval
#bar = 'barval'

## Baz is never a bar
## Defaults to: bazval
#baz = 'bazval'

################################################################################

A good sample of using derpconf can be seen at thumbor's configuration file.

Verifying a Configuration File

derpconf includes a configuration file verifier. The purpose of this verifier is to help you quickly understand what configuration files are missing what keys and what values will be used for them instead.

Running it is as simple as including a call to verify_config in your config.py file:

verify_config(file_path)

Or you can leave it blank and derpconf will get the file path from sys.argv:

verify_config()

The output of the verifier is something like this:

Configuration "baz" not found in file /Users/bernardo/dev/derpconf/vows/fixtures/missing.conf. Using "bazval" instead.
Configuration "foo" not found in file /Users/bernardo/dev/derpconf/vows/fixtures/missing.conf. Using "fooval" instead.
Configuration "bar" not found in file /Users/bernardo/dev/derpconf/vows/fixtures/missing.conf. Using "barval" instead.

You can see it in use at derpconf's code.

License

derpconf is licensed under the MIT License:

The MIT License

Copyright (c) 2012 globo.com timehome@corp.globo.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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