"""
Make argparse.SUPPRESS work as an argument "dest"
 jzwinck suggests
_StoreAction:
 def __call__(self, parser, namespace, values, option_string=None):
-    setattr(namespace, self.dest, values)
+    if self.dest is not argparse.SUPPRESS:
+        setattr(namespace, self.dest, values)
...
"""
import argparse
SUPPRESS = argparse.SUPPRESS
class Action1(argparse._StoreAction):
    # _StoreAction with modified call
    def __call__(self, parser, namespace, values, option_string=None):
        if self.dest is not SUPPRESS:
            setattr(namespace, self.dest, values)
        else:
            print('Action1', argparse._get_action_name(self), values)

class Action2(argparse.Action):
    # custom action
    def __init__(self, *args, **kwargs):
        super(Action2, self).__init__(*args, **kwargs)
        # play with attributes, e.g. dest,
        self.default = SUPPRESS # keeps default out of namespace
        # dist=SUPPRESS also keeps default out of namespace,
        # but affects usage as well
    def __call__(self, parser, namespace, values, option_string=None):
        print('Action2', argparse._get_action_name(self), values)

parser = argparse.ArgumentParser()
a1 = parser.add_argument('--foo', dest=SUPPRESS)
a2 = parser.add_argument('--bar', action=Action1, dest=SUPPRESS,
    type=int)
a3 = parser.add_argument('--baz', action=Action2, type=int)
print(parser.format_help())
print(parser.parse_args([]))
print(parser.parse_args())

"""
usage: issue20430.py [-h] [--foo ==SUPPRESS==] [--bar ==SUPPRESS==]
                     [--baz BAZ]

optional arguments:
  -h, --help          show this help message and exit
  --foo ==SUPPRESS==
  --bar ==SUPPRESS==
  --baz BAZ

Namespace()
Action2 --baz 123
Action1 --bar 456
Namespace(==SUPPRESS==='xxx')
"""