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.
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
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