# HG changeset patch
# User Jeff Hammel <k0scist@gmail.com>
# Date 1417485950 28800
# Node ID c6aea14a3e2be0eaa6c522db42bb2f5a959e1918
# Parent  372315b3bb8eb9764d50ca9185d409cc50248475
wip

diff -r 372315b3bb8e -r c6aea14a3e2b example/argparse_undefined.py
--- a/example/argparse_undefined.py	Thu Nov 06 07:41:05 2014 -0800
+++ b/example/argparse_undefined.py	Mon Dec 01 18:05:50 2014 -0800
@@ -7,7 +7,16 @@
 import argparse
 import sys
 
-class UndefinedArgumentParser(argparse.ArgumentParser)
+class Undefined(object):
+    """singleton"""
+
+Undefined = Undefined()
+
+class UndefinedArgumentParser(argparse.ArgumentParser):
+
+    def add_argument(self, *args, **kwargs):
+        kwargs.setdefault('default', Undefined)
+        return argparse.ArgumentParser.add_argument
 
 def main(args=sys.argv[1:]):