New submission from mike bayer:
this bug appeared in Python 3.4. The inspect.classify_class_attrs compares
the identity objects of unknown type using the `==` operator unnecessarily and
also evaluates objects of unknown type assuming they return `True` for a
straight boolean evaluation. This breaks among other things the ability to use
the help() function with SQLAlchemy mapped objects.
Demo:
class MySpecialObject(object):
def __eq__(self, other):
return MySpecialObject()
def __bool__(self):
raise NotImplementedError(
"This object does not specify a boolean value")
class MyClass(object):
some_thing = MySpecialObject()
import inspect
print(inspect.classify_class_attrs(MyClass))
# ultimate goal: help(MyClass)
A patch here would be to compare unknown objects for identity using the `is`
operator as well as using `is not None` when asserting that an object of
unknown type is non-None. This patch resolves:
--- inspect_orig.py 2015-04-09 10:28:46.000000000 -0400
+++ inspect.py 2015-04-09 10:29:37.000000000 -0400
@@ -380,7 +380,7 @@
# first look in the classes
for srch_cls in class_bases:
srch_obj = getattr(srch_cls, name, None)
- if srch_obj == get_obj:
+ if srch_obj is get_obj:
last_cls = srch_cls
# then check the metaclasses
for srch_cls in metamro:
@@ -388,7 +388,7 @@
srch_obj = srch_cls.__getattr__(cls, name)
except AttributeError:
continue
- if srch_obj == get_obj:
+ if srch_obj is get_obj:
last_cls = srch_cls
if last_cls is not None:
homecls = last_cls
@@ -402,7 +402,7 @@
# unable to locate the attribute anywhere, most likely due to
# buggy custom __dir__; discard and move on
continue
- obj = get_obj or dict_obj
+ obj = get_obj if get_obj is not None else dict_obj
# Classify the object or its descriptor.
if isinstance(dict_obj, staticmethod):
kind = "static method"
----------
components: Library (Lib)
messages: 240331
nosy: zzzeek
priority: normal
severity: normal
status: open
title: inspect() changes in Python3.4 are not compatible with objects that
implement special __bool__, __eq__
versions: Python 3.4
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue23898>
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