This question that I have copied from Stack Overflow clearly states (and expands upon) my motivation for this project. I have made some changes to the original discussion. You can find it at: http://stackoverflow.com/questions/6133517/parse-config-file-environment-and-command-line-arguments-to-get-a-single-coll?answertab=active#tab-top
Python's standard library has modules for configuration file parsing (configparser), environment variable reading (os.environ), and command-line argument parsing (argparse). I want to write a program that does all those, and also:
Has a cascade of option values:
1 default option values, overridden by 2 config file options, overridden by 3 environment variables, overridden by 4 command-line options and finally 5 placing everything into a python data structure for the host program to access.
ADDITIONALLY;
The host program may modify these option values
and then ask that they be saved to the config file
from item 2 above.
Allows a configuration file location specified on the command line with e.g. --config-file foo.conf, and reads that instead of the usual configuration file. This must still obey the above cascade.
Allows option definitions in a single place to determine the parsing behaviour for configuration files and the command line. (EDIT I don't know what the author intended by this. -Conrad Storz)
Everything I need is apparently in the Python standard library, but they don't work together smoothly.
As of 7-16-2015 my project has the ability to manage steps 1 and 2 outlined above using a pair of files formated in a INI style layout.