On May 25, 9:38 pm, Ben Finney <b...@benfinney.id.au> wrote: > Howdy all, > > Python's standard library has modules for configuration file parsing > (configparser) and command-line argument parsing (optparse, argparse). I > want to write a program that does both, but also: > > * Has a cascade of options: default option values, overridden by config > file options, overridden by command-line options. > > * Reads a different, or even additional, configuration file if specified > on the command-line (e.g. --config-file foo.conf) and yet still obeys > the above cascade. > > * Allows a single definition of an option (e.g. logging level) to define > the same option for parsing from configuration files and the command > line. > > * Unifies the parsed options into a single collection for the rest of > the program to access without caring where they came from. > > How can I achieve this with minimum deviation from the Python standard > library?
One thought is start with something like ChainMap, http://code.activestate.com/recipes/305268-chained-map-lookups/?in=user-178123 , or some variant to unify multiple mapping objects into a single prioritized collection. A mapping for command line args can be made by using vars() on an argparse namespace to create a dictionary. ConfigParser's mapping is accessible via its get() method. With a ChainMap style object you can add other option sources such as os.environ. This should get you started on your grand unified, do- everything-at-once vision with minimal deviation from the standard library. Raymond -- http://mail.python.org/mailman/listinfo/python-list
