Closes #12713: Allowed abbreviation of subcommands in argparse.

1 files changed, 18 insertions, 5 deletions

diff --git a/Lib/argparse.py b/Lib/argparse.py
index 209b4e99c1..e0edad8e42 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1110,6 +1110,12 @@ class _SubParsersAction(Action):
         parser_name = values[0]
         arg_strings = values[1:]
 
+        # get full parser_name from (optional) abbreviated one
+        for p in self._name_parser_map:
+            if p.startswith(parser_name):
+                parser_name = p
+                break
+
         # set the parser name if requested
         if self.dest is not SUPPRESS:
             setattr(namespace, self.dest, parser_name)
@@ -2307,11 +2313,18 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
 
     def _check_value(self, action, value):
         # converted value must be one of the choices (if specified)
-        if action.choices is not None and value not in action.choices:
-            args = {'value': value,
-                    'choices': ', '.join(map(repr, action.choices))}
-            msg = _('invalid choice: %(value)r (choose from %(choices)s)')
-            raise ArgumentError(action, msg % args)
+        if action.choices is not None:
+            ac = [ax for ax in action.choices if str(ax).startswith(str(value))]
+            if len(ac) == 0:
+                args = {'value': value,
+                        'choices': ', '.join(map(repr, action.choices))}
+                msg = _('invalid choice: %(value)r (choose from %(choices)s)')
+                raise ArgumentError(action, msg % args)
+            elif len(ac) > 1:
+                args = {'value': value,
+                        'choices': ', '.join(ac)}
+                msg = _('ambiguous choice: %(value)r could match %(choices)s')
+                raise ArgumentError(action, msg % args)
 
     # =======================
     # Help-formatting methods