I've got some Python argparse command-line processing code that initially looked like this:

import argparse

ap = argparse.ArgumentParser()

ap.add_argument("--x", help = "Set `x`.", action = "store_true", default = False)
ap.add_argument("--y", help = "Set `y`.", action = "store_true", default = False)

ap.add_argument(
  "--all", help = "Equivalent to `--x --y`.",
  action = "store_true", default = False
)

args = ap.parse_args()

if args.all:
  args.x = True
  args.y = True

print "args.x", args.x
print "args.y", args.y

The basic idea: I have some boolean flags that toggle on a particular setting (--x, --y, etc), and I want to add a convenience option that toggles multiple settings on - e.g. --all is equivalent to --x --y.

I wanted to avoid having any command-line processing logic that was not contained within the ArgumentParser and done in parse_args, so I came up with this solution using custom argparse.Actions:

import argparse

def store_const_multiple(const, *destinations):
  """Returns an `argparse.Action` class that sets multiple argument
  destinations (`destinations`) to `const`."""
  class store_const_multiple_action(argparse.Action):
    def __init__(self, *args, **kwargs):
      super(store_const_multiple_action, self).__init__(
        metavar = None, nargs = 0, const = const, *args, **kwargs
      )

    def __call__(self, parser, namespace, values, option_string = None):
      for destination in destinations:
        setattr(namespace, destination, const)

  return store_const_multiple_action

def store_true_multiple(*destinations):
  """Returns an `argparse.Action` class that sets multiple argument
  destinations (`destinations`) to `True`."""
  return store_const_multiple(True, *destinations)

ap = argparse.ArgumentParser()

ap.add_argument("--x", help = "Set `x`.", action = "store_true", default = False)
ap.add_argument("--y", help = "Set `y`.", action = "store_true", default = False)

ap.add_argument(
  "--all", help = "Equivalent to `--x --y`.",
  action = store_true_multiple("x", "y")
)

args = ap.parse_args()

print "args.x", args.x
print "args.y", args.y

Is there any clean way of achieving what I want with argparse without either (0) doing some processing after parse_args() (first example) or (2) writing a custom argparse.Action (second example)?