option_maker.py

# saner syntax for optparse add_option

import os
 
def make_option_maker(parser, cmdline_prefix="", env_prefix="", dest_prefix=""):
    """Return a function that can be used to add_option with saner syntax.
 
    Arguments:
      parser: the parser object that will be used by the returned function
      cmdline_prefix: will be used together with the name to build the command
          line option. a suffix of -- and a prefix of - will be added so you
          do not need to include those (--cmdline_prefix-<name>)
      env_prefix: will be used together with the name to specify the environment
          variable from which the option will default (ENV_PREFIX_<NAME>)
      dest_prefix: will be used together with name to specify the variable name
          in which the value of the option will be stored
 
    Example:
      parser = OptionParser()
      omaker = make_option_maker(parser, dest_prefix = "someprefix",
                                   env_prefix = "SOMEPREFIX",
                                   cmdline_prefix = "someprefix")
 
      omaker('foo', action="append", help="collect a list of foo")
      omaker('bar', help="store bar", default="Blah")
    """
    
    env_prefix = env_prefix.upper()
    
    if cmdline_prefix and not cmdline_prefix.endswith("-"):
        cmdline_prefix += "-"
 
    if env_prefix and not env_prefix.endswith("_"):
        env_prefix += "_"
 
    if dest_prefix and not dest_prefix.endswith("_"):
        dest_prefix += "_"
        
    def option_maker(name, action = "store", help = "", default = None):
        """Use the given name, action and help string to add an option"""
 
        if default is None:
            _default = os.environ.get(env_prefix + name.upper())
        else:
            _default = default
            
        parser.add_option("--" + cmdline_prefix + name.lower(),
                          action = action, dest = dest_prefix + name.lower(),
                          default= _default,
                          help = help + " [" + env_prefix + name.upper() + "]")
 
    return option_maker