pesky-defaults 0.0.2

Pesky configuration defaults interface

pesky-defaults is a small library for querying platform, distribution, and package defaults using a uniform interface.

The following default keys are made accessible and their values set according to the detected platform:

• PREFIX

• BIN_DIR

• SBIN_DIR

• LIB_DIR

• LIBEXEC_DIR

• SYSCONF_DIR

• LOCALSTATE_DIR

• RUN_DIR

• DATA_DIR

A setuptools command is also provided (‘pesky_default’) so that project defaults can be specified, potentially overriding platform or distribution defaults.

Basic Usage

To use pesky-defaults, simply instantiate a new Defaults object and invoke the query methods ‘get’ or ‘getorelse’:

from pesky.defaults import Defaults
defaults = Defaults()
print defaults.get('PREFIX')    # displays /usr on a linux platform

The Defaults class implements the collections.Mapping interface, so you can use the familiar mapping methods as well:

print defaults['LIB_DIR']       # displays /usr/lib on a linux platform

Project Defaults

If you specify a project name when instantiating the Defaults object, then all defaults from the project metadata will be loaded as well:

from pesky.defaults import Defaults
defaults = Defaults('my-project')   # the project name as given to setuptools

This is all well and good, but how do the project defaults get set in the first place? This is where the ‘pesky_default’ setuptools command comes into play. By invoking the ‘pesky_default’ setuptools command, the .egg-info file called ‘pesky_defaults.json’ is manipulated. Once all project defaults are set as desired, the ‘install’ setuptools command can be invoked, which will perform the standard setuptools install routine and copy all egg-info files into place. For example:

$ cd my-project/
$ python ./setup.py pesky_default --command set --key foo --value bar
$ python ./setup.py install

This snippet enters the source tree of the fictional project ‘my-project’, adds the project default ‘foo’, giving it the value ‘bar’, then installs the project (with the updated project defaults). The application code can then retrieve the ‘foo’ default:

from pesky.defaults import Defaults
defaults = Defaults('my-project')   # the project name as given to setuptools
print defaults.get('foo')           # displays bar