b3j0f.conf 0.2.3

python class configuration tools useful in python projects.

Description

Python class configuration tools in reflective and distributed concerns.

Links

• Homepage

• PyPI

• Documentation

Installation

pip install b3j0f.conf

Features

This library provides a set of class configuration tools in order to ease development of systems based on configuration resources such as files, DB documents, etc. in a reflexive context.

Configuration process is in 2 steps:

• inject configuration resources (file, DB documents, etc.) in a Configurable class (with specific drivers which allows the Configurable class to be agnostic from configuration languages such as ini, json, xml, etc.),

• let the configurable class read properties from such configuration resources and apply values on a dedicated class which may be a associated to a business code. This last process can be done automatically or manually thanks to the the applyconfiguration method.

Configuration

The sub-module b3j0f.conf.model provides Configuration class in order to inject configuration resources in a configurable class.

Configuration resources respect two levels of configuration same as the ini configuration model. Both levels are respectively:

• Category: permits to define a set of parameters unique by name.

• Parameter: couple of property name and value.

And all categories/parameters are embedded in a Configuration class.

Configuration and Categories are like dictionaries where key values are inner element names. Therefore, Parameter names are unique per Categories, and Category/Parameter names are unique per Configuration.

Parameter Overriding

In a dynamic and complex way, one Configurable class can be bound to several Categories and Parameters. The choice is predetermined by the class itself. That means that one Configurable class can use several configuration resources and all/some/none Categories/Parameters in those resources. In such a way, the order is important because it permits to keep only last parameter values when parameters have the same name.

This overriding is respected by default with Configurable class inheritance. That means a sub class which adds a resource after its parent class resources indicates than all parameters in the final resources will override parameters in the parent class resources where names are the sames.

Name such as a regular expression

Even if a parameter uses a name, it is possible to use this name such as a regular expression name.

In this case, while reading a configuration from a resource, all configuration parameters which match the regular expression will use the same attributes as defined in the parameter with the regular expression. And a name which is the name from the configuration resource.

Parser

The module b3j0f.conf.model.parser provides parsers used to deserialize parameter values.

Default parser is the expression parser.

Expression parser

The parser exprparser permits to write simple expressions using the python builtin functions except those able to do I/O operations like the open function.

Such expression is prefixed by the character =.

In such expression, you can call back other configuration parameter in using this format (thanks to the idea from the pypi config project) related to a Configuration model:

• #{path} where path corresponds to a python object path. For example, #sys.maxsize designates the max size of the integer on the host machine (attribute maxsize of the module sys).

• @[[://{path}/]{cat}].{param} where cat designates a configuration category name, and param designates related parameter value.

• @{param} where param designates a final parameter value (last overidden value).

Configurable

A Configurable class is provided in the b3j0f.conf.configurable.core module. It permits to get parameters from a configuration resources.

It uses a Configuration model and drivers.

Driver

Drivers are the mean to parse configuration resources, such as files, etc. from a configuration model provided by a Configurable object. By default, conf drivers are able to parse json/ini files. Those last use a relative path given by the environment variable B3J0F_CONF_DIR or from directories (in this order) /etc, /usr/local/etc, ~/etc, ~/.config, ~/config or current execution directory.

Example

Bind configuration files to an object

Bind the configuration file ~/etc/myclass.conf and ~/.config/myclass.conf to a business class MyClass (the relative path ~/etc can be change thanks to the environment variable B3J0F_CONF_DIR).

The configuration file contains a category named MYCLASS containing the parameters:

• myattr equals 'myvalue'.

• six equals 6.

• twelve equals six * 2.0.

Let the following configuration file ~/etc/myclass.conf in ini format:

[MYCLASS]
myattr = myvalue
twelve = = @six * 2.0

Let the following configuration file ~/.config/myclass.conf in json format:

{
  "MYCLASS": {
    "six": 6
  }
}

The following code permits to load upper configuration to a python object.

from b3j0f.conf import Configurable, Category

# instantiate a business class
@Configurable(paths='myclass.conf', conf=Category('MYCLASS'))
class MyClass(object):
    pass

myclass = MyClass()

# assert attributes
assert myclass.myattr == 'myvalue'
assert myclass.six == 6
assert myclass.twelve == 12

Configure several objects with one configurable

from b3j0f.conf import getconfigurables

class Test(object):
    pass

toconfigure = list(Test() for _ in range(5))

configurable = getconfigurables(myclass)
configurable.applyconfiguration(toconfigure=toconfigure)

for item in toconfigure:
    assert item.six == 6

Reconfigure a configurable object

from b3j0f.conf import applyconfiguration

myclass.six = 7

applyconfiguration(myclass)

assert myclass.six == 6

Perspectives

• wait feedbacks during 6 months before passing it to a stable version.

• Cython implementation.

Donation