Allow single character options, e.g. '-' and '+'.

3 files changed, 31 insertions, 19 deletions

diff --git a/NEWS.txt b/NEWS.txt
index c4859b5..98c7139 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -8,6 +8,7 @@ What's New in argparse 1.1
 - Issue #38: Better error messages when 'dest' occurs twice for positional arguments.
 - Issue #39: Better error messages for invalid actions.
 - Issue #43: Deprecate ArgumentParser(..., version=XXX, ...) and friends.
+- Issue #46: Allow single character options, e.g. '-' and '+'.
 - Namespace objects now support "in" (i.e. __contains__).
 - Usage and help (but not version) messages are written to stdout, not stderr.
 
diff --git a/argparse.py b/argparse.py
index fd21104..c89618b 100644
--- a/argparse.py
+++ b/argparse.py
@@ -1394,12 +1394,6 @@ class _ActionsContainer(object):
         option_strings = []
         long_option_strings = []
         for option_string in args:
-            # error on one-or-fewer-character option strings
-            if len(option_string) < 2:
-                msg = _('invalid option string %r: '
-                        'must be at least two characters long')
-                raise ValueError(msg % option_string)
-
             # error on strings that don't start with an appropriate prefix
             if not option_string[0] in self.prefix_chars:
                 msg = _('invalid option string %r: '
@@ -1407,18 +1401,12 @@ class _ActionsContainer(object):
                 tup = option_string, self.prefix_chars
                 raise ValueError(msg % tup)
 
-            # error on strings that are all prefix characters
-            if not (_set(option_string) - _set(self.prefix_chars)):
-                msg = _('invalid option string %r: '
-                        'must contain characters other than %r')
-                tup = option_string, self.prefix_chars
-                raise ValueError(msg % tup)
-
             # strings starting with two prefix characters are long options
             option_strings.append(option_string)
             if option_string[0] in self.prefix_chars:
-                if option_string[1] in self.prefix_chars:
-                    long_option_strings.append(option_string)
+                if len(option_string) > 1:
+                    if option_string[1] in self.prefix_chars:
+                        long_option_strings.append(option_string)
 
         # infer destination, '--foo-bar' -> 'foo_bar' and '-x' -> 'x'
         dest = kwargs.pop('dest', None)
@@ -1428,6 +1416,9 @@ class _ActionsContainer(object):
             else:
                 dest_option_string = option_strings[0]
             dest = dest_option_string.lstrip(self.prefix_chars)
+            if not dest:
+                msg = _('dest= is required for options like %r')
+                raise ValueError(msg % option_string)
             dest = dest.replace('-', '_')
 
         # return the updated keyword arguments
@@ -2043,15 +2034,15 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         if not arg_string[0] in self.prefix_chars:
             return None
 
-        # if it's just dashes, it was meant to be positional
-        if not arg_string.strip('-'):
-            return None
-
         # if the option string is present in the parser, return the action
         if arg_string in self._option_string_actions:
             action = self._option_string_actions[arg_string]
             return action, arg_string, None
 
+        # if it's just a single character, it was meant to be positional
+        if len(arg_string) == 1:
+            return None
+
         # if the option string before the "=" is present, return the action
         if '=' in arg_string:
             option_string, explicit_arg = arg_string.split('=', 1)
diff --git a/test/test_argparse.py b/test/test_argparse.py
index 290b5e9..968843c 100644
--- a/test/test_argparse.py
+++ b/test/test_argparse.py
@@ -125,6 +125,7 @@ class NS(object):
 class ArgumentParserError(Exception):
 
     def __init__(self, message, stdout=None, stderr=None, error_code=None):
+        Exception.__init__(self, message, stdout, stderr)
         self.message = message
         self.stdout = stdout
         self.stderr = stderr
@@ -1204,6 +1205,25 @@ class TestEmptyAndSpaceContainingArguments(ParserTestCase):
     ]
 
 
+class TestPrefixCharacterOnlyArguments(ParserTestCase):
+
+    parser_signature = Sig(prefix_chars='-+')
+    argument_signatures = [
+        Sig('-', dest='x', nargs='?', const='badger'),
+        Sig('+', dest='y', type=int, default=42),
+        Sig('-+-', dest='z', action='store_true'),
+    ]
+    failures = ['-y', '+ -']
+    successes = [
+        ('', NS(x=None, y=42, z=False)),
+        ('-', NS(x='badger', y=42, z=False)),
+        ('- X', NS(x='X', y=42, z=False)),
+        ('+ -3', NS(x=None, y=-3, z=False)),
+        ('-+-', NS(x=None, y=42, z=True)),
+        ('- ===', NS(x='===', y=42, z=False)),
+    ]
+
+
 class TestNargsZeroOrMore(ParserTestCase):
     """Tests specifying an args for an Optional that accepts zero or more"""