Skip to content

"inspect" gets broken by some descriptors #46118

Closed
Closed
"inspect" gets broken by some descriptors#46118
Labels
stdlibStandard Library Python modules in the Lib/ directorytype-bugAn unexpected behavior, bug, or error

Description

@d-maurer
d-maurer
mannequin
opened on Jan 10, 2008
BPO 1785
Nosy @gvanrossum, @facundobatista, @d-maurer, @amauryfa, @pitrou, @merwok, @meadori, @ericsnowcurrently, @vpelletier
Files
  • inspectBug.py
  • inspect-bug.patch
  • inspect-and-pydoc-bug.patch
  • inspect-and-pydoc-bug2.patch
  • inspect-and-pydoc-bug3.patch
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

    Show more details

    GitHub fields:

    assignee = None
closed_at = <Date 2011-12-21.09:19:07.701>
created_at = <Date 2008-01-10.17:39:24.074>
labels = ['type-bug', 'library']
title = '"inspect" gets broken by some descriptors'
updated_at = <Date 2012-01-18.16:46:09.842>
user = 'https://github.com/d-maurer'

    bugs.python.org fields:

    activity = <Date 2012-01-18.16:46:09.842>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2011-12-21.09:19:07.701>
closer = 'pitrou'
components = ['Library (Lib)']
creation = <Date 2008-01-10.17:39:24.074>
creator = 'dmaurer'
dependencies = []
files = ['9117', '9119', '9128', '23975', '23976']
hgrepos = []
issue_num = 1785
keywords = ['patch']
message_count = 20.0
messages = ['59675', '59676', '59677', '59684', '59712', '59743', '67777', '116863', '149242', '149606', '149607', '149968', '149970', '149973', '150005', '151544', '151545', '151548', '151549', '151550']
nosy_count = 13.0
nosy_names = ['gvanrossum', 'facundobatista', 'dmaurer', 'amaury.forgeotdarc', 'pitrou', 'flub', 'eric.araujo', 'meador.inge', 'jotr', 'BreamoreBoy', 'python-dev', 'eric.snow', 'vpelletier']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1785'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']

    Activity

    1. d-maurer commented on Jan 10, 2008

      @d-maurer
      d-maurermannequin
      on Jan 10, 2008
      MannequinAuthor

      The inspect functions "getmembers(cls)" and "classify_class_attrs(cls)"
      require that for a class *cls* each name in "dir(cls)" can be retrieved
      by "getattr(cls, name)". While this holds for usual class attributes, it
      may well fail for descriptors (descriptors set by 'zope.interface' are a
      real world example for this). Attached it as small script that
      demonstrates the problem.

      The bug affects 'pydoc' and the built in 'help' (which is in fact
      'pydoc.help'). While 'pydoc' and 'help' do not break completely, they
      can not present meaningful information for classes with some descriptors

    2. d-maurer
      added
      stdlibStandard Library Python modules in the Lib/ directory
      type-bugAn unexpected behavior, bug, or error
      on Jan 10, 2008

    3. gvanrossum commented on Jan 10, 2008

      @gvanrossum
      gvanrossum
      on Jan 10, 2008
      Member

      Please submit a patch.

    4. d-maurer commented on Jan 10, 2008

      @d-maurer
      d-maurermannequin
      on Jan 10, 2008
      MannequinAuthor

      In "dm.zdoc" (a "pydoc" wrapper for Zope) I simply filter out all names
      returned by "dir" which cannot be "getattr"ed.
      But, I am not sure, that this is good enough to be accepted as a patch
      (although it already improves upon the current state)

    5. pitrou commented on Jan 10, 2008

      @pitrou
      pitrou
      on Jan 10, 2008
      Member

      This is my attempt at a patch for this. It fixes inspect.getmembers and
      inspect.classify_class_attrs to work with Dieter's example. I hope it
      doesn't mess anything else.

      As for pydoc, things look a bit more complicated... The annoying thing
      is that the logic to browse object contents is duplicated inside the
      different renderers (pydoc.Repr subclasses). Also, I couldn't find any
      unit tests for pydoc. Are there any?

    6. pitrou commented on Jan 11, 2008

      @pitrou
      pitrou
      on Jan 11, 2008
      Member

      For the record the same problem also happens with toscawidgets.

      >>> from toscawidgets.widgets.forms import validators
>>> help(validators)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/site.py", line 351, in __call__
    return pydoc.help(*args, **kwds)
  File "/usr/lib/python2.5/pydoc.py", line 1646, in __call__
    self.help(request)
  File "/usr/lib/python2.5/pydoc.py", line 1690, in help
    else: doc(request, 'Help on %s:')
  File "/usr/lib/python2.5/pydoc.py", line 1481, in doc
    pager(title % desc + '\n\n' + text.document(object, name))
  File "/usr/lib/python2.5/pydoc.py", line 324, in document
    if inspect.ismodule(object): return self.docmodule(*args)
  File "/usr/lib/python2.5/pydoc.py", line 1072, in docmodule
    contents.append(self.document(value, key, name))
  File "/usr/lib/python2.5/pydoc.py", line 325, in document
    if inspect.isclass(object): return self.docclass(*args)
  File "/usr/lib/python2.5/pydoc.py", line 1173, in docclass
    classify_class_attrs(object))
  File "/usr/lib/python2.5/pydoc.py", line 179, in classify_class_attrs
    return map(fixup, inspect.classify_class_attrs(object))
  File "/usr/lib/python2.5/inspect.py", line 246, in classify_class_attrs
    obj = getattr(cls, name)
  File
"/usr/lib/python2.5/site-packages/FormEncode-0.7.1-py2.5.egg/formencode/declarative.py",
line 105, in __get__
    obj = type.singleton()
  File
"/usr/lib/python2.5/site-packages/FormEncode-0.7.1-py2.5.egg/formencode/declarative.py",
line 166, in singleton
    setattr(cls, name, cls(declarative_count=cls.declarative_count))
TypeError: __init__() got an unexpected keyword argument 'declarative_count'

    7. pitrou commented on Jan 11, 2008

      @pitrou
      pitrou
      on Jan 11, 2008
      Member

      Here is a (hopefully complete) patch against both pydoc and inspect. It
      fixes one more bug compared to the previous one (descriptors can also
      have a special __getattr__ in addition to __get__, which gave problems
      when trying to access __classobj__).

    8. jafo
      assigned
      facundobatista
      on Mar 18, 2008

    9. facundobatista commented on Jun 6, 2008

      @facundobatista
      facundobatista
      on Jun 6, 2008
      Member

      Really don't know why this was assigned to me...

    10. facundobatista
      removed their assignment
      on Jun 6, 2008

    11. BreamoreBoy commented on Sep 19, 2010

      @BreamoreBoy
      BreamoreBoymannequin
      on Sep 19, 2010
      Mannequin

      I can't apply the patch to any current SVN version.

    12. amauryfa commented on Dec 11, 2011

      @amauryfa
      amauryfa
      on Dec 11, 2011
      Contributor

      The 'type' object now has the same issue: __abstractmethods__ appears in dir(type) but type.__abstractmethods__ fails with an AttributeError.
      See bpo-13581

    13. pitrou commented on Dec 16, 2011

      @pitrou
      pitrou
      on Dec 16, 2011
      Member

      Updated patch for 3.2.

    14. pitrou commented on Dec 16, 2011

      @pitrou
      pitrou
      on Dec 16, 2011
      Member

      Updated patch that adds a test for classifying builtin types (checks that inspect.classify_class_attrs(type) does not throw as in bpo-13581).

    15. python-dev commented on Dec 21, 2011

      @python-dev
      python-devmannequin
      on Dec 21, 2011
      Mannequin

      New changeset 902f694a7b0e by Antoine Pitrou in branch '3.2':
      Issue bpo-1785: Fix inspect and pydoc with misbehaving descriptors.
      http://hg.python.org/cpython/rev/902f694a7b0e

      New changeset b08bf8df8eec by Antoine Pitrou in branch 'default':
      Issue bpo-1785: Fix inspect and pydoc with misbehaving descriptors.
      http://hg.python.org/cpython/rev/b08bf8df8eec

    16. python-dev commented on Dec 21, 2011

      @python-dev
      python-devmannequin
      on Dec 21, 2011
      Mannequin

      New changeset 13f56cd8dec1 by Antoine Pitrou in branch '2.7':
      Issue bpo-1785: Fix inspect and pydoc with misbehaving descriptors.
      http://hg.python.org/cpython/rev/13f56cd8dec1

    17. pitrou commented on Dec 21, 2011

      @pitrou
      pitrou
      on Dec 21, 2011
      Member

      Now fixed in all 3 branches.

    18. pitrou
      closed this as completedon Dec 21, 2011

    19. merwok commented on Dec 21, 2011

      @merwok
      merwok
      on Dec 21, 2011
      Member

      Great stuff.

    20. vpelletier commented on Jan 18, 2012

      @vpelletier
      vpelletiermannequin
      on Jan 18, 2012
      Mannequin

      This change causes the following behaviour:

      >>> import inspect
>>> class B(object):
...   def f(self):
...     pass
... 
>>> inspect.getmembers(B, inspect.ismethod)
[]

      While I would expect the result to contain f:

      >>> inspect.ismethod(B.f)
True

      Isn't this a regression ?

      Regards,
      Vincent Pelletier

    21. vpelletier commented on Jan 18, 2012

      @vpelletier
      vpelletiermannequin
      on Jan 18, 2012
      Mannequin

      Sorry, I forgot to mention I'm using python2.7 .

    22. pitrou commented on Jan 18, 2012

      @pitrou
      pitrou
      on Jan 18, 2012
      Member

      Thanks for noticing. The doc for ismethod() says:

      “Return true if the object is a bound method written in Python.”

      and the docstring agrees with that:

      “Return true if the object is an instance method. [...]”

      So the change isn't properly a regression when reading the docs. On the other hand, it's true that some code may rely on the previous behaviour, and the discrepancy between getmembers() and a manual test can be confusing.

      By the way, Python 3 has ismethod() right:

      >>> class B:
...   def f(self): pass
... 
>>> inspect.ismethod(B.f)
False
>>> inspect.ismethod(B().f)
True

    23. python-dev commented on Jan 18, 2012

      @python-dev
      python-devmannequin
      on Jan 18, 2012
      Mannequin

      New changeset f824744557ba by Antoine Pitrou in branch '2.7':
      Revert part of 13f56cd8dec1 (issue bpo-1785) to avoid breaking getmembers() with unbound methods.
      http://hg.python.org/cpython/rev/f824744557ba

    24. pitrou commented on Jan 18, 2012

      @pitrou
      pitrou
      on Jan 18, 2012
      Member

      I've backed out the part of the changeset that "fixed" getmembers(), so the old behaviour is restored. Other parts of the changeset (that e.g. fixed pydoc) have not been reverted.

    25. ezio-melotti
      transferred this issue fromon Apr 10, 2022
    Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

    Metadata

    Metadata

    Assignees

    No one assigned

      Labels

      stdlibStandard Library Python modules in the Lib/ directorytype-bugAn unexpected behavior, bug, or error

      Projects

      No projects

        Milestone

        No milestone

        Relationships

        None yet

        Development

        No branches or pull requests

        Issue actions