From be051b2738ef9e459651e3c75a24f0ce97374d0c Mon Sep 17 00:00:00 2001
From: "steven.bethard" <devnull@localhost>
Date: Mon, 13 Jul 2009 00:02:35 +0000
Subject: Add ArgumentDefaultsHelpFormatter.

---
 argparse.py                   | 17 ++++++++++++++++-
 doc/source/ArgumentParser.rst | 21 +++++++++++++++++++++
 test/test_argparse.py         | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/argparse.py b/argparse.py
index 4ae1c89..8ee556b 100644
--- a/argparse.py
+++ b/argparse.py
@@ -549,7 +549,7 @@ class HelpFormatter(object):
         if params.get('choices') is not None:
             choices_str = ', '.join([str(c) for c in params['choices']])
             params['choices'] = choices_str
-        return action.help % params
+        return self._get_help_string(action) % params
 
     def _iter_indented_subactions(self, action):
         try:
@@ -571,6 +571,9 @@ class HelpFormatter(object):
         return _textwrap.fill(text, width, initial_indent=indent,
                                            subsequent_indent=indent)
 
+    def _get_help_string(self, action):
+        return action.help
+
 
 class RawDescriptionHelpFormatter(HelpFormatter):
 
@@ -584,6 +587,18 @@ class RawTextHelpFormatter(RawDescriptionHelpFormatter):
         return text.splitlines()
 
 
+class ArgumentDefaultsHelpFormatter(HelpFormatter):
+
+    def _get_help_string(self, action):
+        help = action.help
+        if '%(default)' not in action.help:
+            if action.default is not SUPPRESS:
+                defaulting_nargs = [OPTIONAL, ZERO_OR_MORE]
+                if action.option_strings or action.nargs in defaulting_nargs:
+                    help += ' (default: %(default)s)'
+        return help
+
+
 # =====================
 # Options and Arguments
 # =====================
diff --git a/doc/source/ArgumentParser.rst b/doc/source/ArgumentParser.rst
index 1bf5e63..8a103dd 100644
--- a/doc/source/ArgumentParser.rst
+++ b/doc/source/ArgumentParser.rst
@@ -176,6 +176,10 @@ Sometimes, several parsers share a common set of arguments. Rather than repeatin
 formatter_class
 ---------------
 
+ArgumentParser objects allow the help formatting to be customized by specifying an alternate formatting class.
+Currently, there are three such classes: ``argparse.RawDescriptionHelpFormatter``, ``argparse.RawTextHelpFormatter`` and ``argparse.ArgumentDefaultsHelpFormatter``.
+The first two allow more control over how textual descriptions are displayed, while the last automatically adds information about argument default values.
+
 By default, ArgumentParser objects line-wrap the description_ and epilog_ texts in command-line help messages::
 
   >>> parser = argparse.ArgumentParser(
@@ -224,6 +228,23 @@ When you have description_ and epilog_ that is already correctly formatted and s
 
 If you want to maintain whitespace for all sorts of help text (including argument descriptions), you can use ``argparse.RawTextHelpFormatter``.
 
+The other formatter class available, ``argparse.ArgumentDefaultsHelpFormatter``, will add information about the default value of each of the arguments::
+
+  >>> parser = argparse.ArgumentParser(
+  ...     prog='PROG',
+  ...     formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+  >>> parser.add_argument('--foo', type=int, default=42, help='FOO!')
+  >>> parser.add_argument('bar', nargs='*', default=[1, 2, 3], help='BAR!')
+  >>> parser.print_help()
+  usage: PROG [-h] [--foo FOO] [bar [bar ...]]
+
+  positional arguments:
+    bar         BAR! (default: [1, 2, 3])
+
+  optional arguments:
+    -h, --help  show this help message and exit
+    --foo FOO   FOO! (default: 42)
+
 
 conflict_handler
 ----------------
diff --git a/test/test_argparse.py b/test/test_argparse.py
index 33bec2d..67026d9 100644
--- a/test/test_argparse.py
+++ b/test/test_argparse.py
@@ -3176,6 +3176,47 @@ class TestHelpRawDescription(HelpTestCase):
         '''
     version = ''
 
+
+class TestHelpArgumentDefaults(HelpTestCase):
+    """Test the ArgumentDefaultsHelpFormatter"""
+
+    parser_signature = Sig(
+        prog='PROG', formatter_class=argparse.ArgumentDefaultsHelpFormatter,
+        description='description')
+
+    argument_signatures = [
+        Sig('--foo', help='foo help - oh and by the way, %(default)s'),
+        Sig('--bar', action='store_true', help='bar help'),
+        Sig('spam', help='spam help'),
+        Sig('badger', nargs='?', default='wooden', help='badger help'),
+    ]
+    argument_group_signatures = [
+        (Sig('title', description='description'),
+         [Sig('--baz', type=int, default=42, help='baz help')]),
+    ]
+    usage = '''\
+        usage: PROG [-h] [--foo FOO] [--bar] [--baz BAZ] spam [badger]
+        '''
+    help = usage + '''\
+
+        description
+
+        positional arguments:
+          spam        spam help
+          badger      badger help (default: wooden)
+
+        optional arguments:
+          -h, --help  show this help message and exit
+          --foo FOO   foo help - oh and by the way, None
+          --bar       bar help (default: False)
+
+        title:
+          description
+
+          --baz BAZ   baz help (default: 42)
+        '''
+    version = ''
+
 # =====================================
 # Optional/Positional constructor tests
 # =====================================
-- 
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