René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"rlcompleter suggests attributes not accessible on instances (e.g., Enum member __name__)","articleBody":"# Bug report\n\n### Bug description:\n\nWhile looking into gh-139398, I noticed a separate issue: some tab-completion suggestions are offered even though they do not actually exist / are not accessible.\n\nFor example, on an Enum member, `__name__` is suggested but accessing it raises AttributeError. Tracing the behavior shows rlcompleter includes class-level names even when they aren’t accessible from the instance; adding a guard in rlcompleter fixes it (PR incoming).\n\n#### Reproduce\n\n```python\nfrom enum import Enum\nclass Color(Enum):\n    BLUE = 1\n\n# In the REPL, press \u003cTAB\u003e after typing:\nColor.BLUE.__\n# '__name__' appears in the suggestions.\n\nColor.BLUE.__name__  # AttributeError: 'Color' object has no attribute '__name__'\n```\n\n#### Expected\nOnly attributes actually accessible on the instance should be suggested.\n\n#### Actual\nClass-level names show up for instances (e.g., Enum members), leading to AttributeError when accessed.\n\n#### Fix\n\n```diff\ndiff --git a/Lib/rlcompleter.py b/Lib/rlcompleter.py\nindex 23eb0020f42..521f41a869d 100644\n--- a/Lib/rlcompleter.py\n+++ b/Lib/rlcompleter.py\n@@ -39,6 +39,9 @@\n\n __all__ = [\"Completer\"]\n\n+# Sentinel object to distinguish \"missing\" from \"present but None\"\n+_SENTINEL = object()\n+\n class Completer:\n     def __init__(self, namespace = None):\n         \"\"\"Create a new completer for the command line.\n@@ -188,9 +191,9 @@ def attr_matches(self, text):\n                         # property method, which is not desirable.\n                         matches.append(match)\n                         continue\n-                    if (value := getattr(thisobject, word, None)) is not None:\n+                    if (value := getattr(thisobject, word, _SENTINEL)) is not _SENTINEL:\n                         matches.append(self._callable_postfix(value, match))\n-                    else:\n+                    elif word in getattr(type(thisobject), '__slots__', ()):\n                         matches.append(match)\n             if matches or not noprefix:\n                 break\n```\n\n#### Also observed (bogus suggestions)\n```\n['Color.BLUE.__iter__',\n 'Color.BLUE.__getitem__',\n 'Color.BLUE.__members__',\n 'Color.BLUE.__contains__',\n 'Color.BLUE.__qualname__',\n 'Color.BLUE.__len__',\n 'Color.BLUE.__name__']\n# Additionally seen among bogus suggestions:\n'Enum.__abstractmethods__'\n```\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nmacOS\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-139820\n* gh-151222\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/ttw225","@type":"Person","name":"ttw225"},"datePublished":"2025-10-09T03:53:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/139819/cpython/issues/139819"}