bpo-38530: Offer suggestions on AttributeError (#16856) · wrongnull/cpython@37494b4 · GitHub
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bpo-38530: Offer suggestions on AttributeError (python#16856)
When printing AttributeError, PyErr_Display will offer suggestions of similar attribute names in the object that the exception was raised from: >>> collections.namedtoplo Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple?
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12 files changed

Lines changed: 470 additions & 15 deletions

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‎Doc/library/exceptions.rst‎

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‎Doc/whatsnew/3.10.rst‎

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@@ -125,8 +125,11 @@ Check :pep:`617` for more details.
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in :issue:`12782` and :issue:`40334`.)
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Better error messages in the parser
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-----------------------------------
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Better error messages
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---------------------
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SyntaxErrors
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~~~~~~~~~~~~
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When parsing code that contains unclosed parentheses or brackets the interpreter
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now includes the location of the unclosed bracket of parentheses instead of displaying
@@ -167,6 +170,23 @@ These improvements are inspired by previous work in the PyPy interpreter.
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(Contributed by Pablo Galindo in :issue:`42864` and Batuhan Taskaya in
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:issue:`40176`.)
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AttributeErrors
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~~~~~~~~~~~~~~~
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When printing :exc:`AttributeError`, :c:func:`PyErr_Display` will offer
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suggestions of simmilar attribute names in the object that the exception was
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raised from:
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.. code-block:: python
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>>> collections.namedtoplo
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple?
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(Contributed by Pablo Galindo in :issue:`38530`.)
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PEP 626: Precise line numbers for debugging and other tools
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-----------------------------------------------------------
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‎Include/cpython/pyerrors.h‎

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@@ -62,6 +62,12 @@ typedef struct {
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PyObject *value;
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} PyStopIterationObject;
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typedef struct {
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PyException_HEAD
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PyObject *obj;
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PyObject *name;
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} PyAttributeErrorObject;
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/* Compatibility typedefs */
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typedef PyOSErrorObject PyEnvironmentErrorObject;
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#ifdef MS_WINDOWS

‎Include/internal/pycore_pyerrors.h‎

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@@ -86,6 +86,8 @@ PyAPI_FUNC(int) _PyErr_CheckSignalsTstate(PyThreadState *tstate);
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PyAPI_FUNC(void) _Py_DumpExtensionModules(int fd, PyInterpreterState *interp);
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extern PyObject* _Py_Offer_Suggestions(PyObject* exception);
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#ifdef __cplusplus
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}
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#endif

‎Lib/test/test_exceptions.py‎

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@@ -1414,6 +1414,165 @@ class TestException(MemoryError):
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gc_collect()
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class AttributeErrorTests(unittest.TestCase):
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def test_attributes(self):
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# Setting 'attr' should not be a problem.
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exc = AttributeError('Ouch!')
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self.assertIsNone(exc.name)
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self.assertIsNone(exc.obj)
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sentinel = object()
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exc = AttributeError('Ouch', name='carry', obj=sentinel)
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self.assertEqual(exc.name, 'carry')
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self.assertIs(exc.obj, sentinel)
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def test_getattr_has_name_and_obj(self):
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class A:
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blech = None
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obj = A()
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try:
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obj.bluch
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except AttributeError as exc:
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self.assertEqual("bluch", exc.name)
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self.assertEqual(obj, exc.obj)
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def test_getattr_has_name_and_obj_for_method(self):
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class A:
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def blech(self):
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return
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obj = A()
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try:
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obj.bluch()
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except AttributeError as exc:
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self.assertEqual("bluch", exc.name)
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self.assertEqual(obj, exc.obj)
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def test_getattr_suggestions(self):
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class Substitution:
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noise = more_noise = a = bc = None
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blech = None
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class Elimination:
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noise = more_noise = a = bc = None
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blch = None
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class Addition:
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noise = more_noise = a = bc = None
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bluchin = None
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class SubstitutionOverElimination:
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blach = None
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bluc = None
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class SubstitutionOverAddition:
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blach = None
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bluchi = None
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class EliminationOverAddition:
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blucha = None
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bluc = None
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for cls, suggestion in [(Substitution, "blech?"),
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(Elimination, "blch?"),
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(Addition, "bluchin?"),
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(EliminationOverAddition, "bluc?"),
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(SubstitutionOverElimination, "blach?"),
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(SubstitutionOverAddition, "blach?")]:
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try:
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cls().bluch
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertIn(suggestion, err.getvalue())
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def test_getattr_suggestions_do_not_trigger_for_long_attributes(self):
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class A:
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blech = None
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try:
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A().somethingverywrong
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertNotIn("blech", err.getvalue())
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def test_getattr_suggestions_do_not_trigger_for_big_dicts(self):
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class A:
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blech = None
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# A class with a very big __dict__ will not be consider
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# for suggestions.
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for index in range(101):
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setattr(A, f"index_{index}", None)
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try:
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A().bluch
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertNotIn("blech", err.getvalue())
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def test_getattr_suggestions_no_args(self):
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class A:
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blech = None
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def __getattr__(self, attr):
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raise AttributeError()
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try:
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A().bluch
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertIn("blech", err.getvalue())
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class A:
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blech = None
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def __getattr__(self, attr):
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raise AttributeError
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try:
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A().bluch
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertIn("blech", err.getvalue())
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def test_getattr_suggestions_invalid_args(self):
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class NonStringifyClass:
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__str__ = None
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__repr__ = None
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class A:
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blech = None
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def __getattr__(self, attr):
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raise AttributeError(NonStringifyClass())
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class B:
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blech = None
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def __getattr__(self, attr):
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raise AttributeError("Error", 23)
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class C:
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blech = None
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def __getattr__(self, attr):
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raise AttributeError(23)
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for cls in [A, B, C]:
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try:
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cls().bluch
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except AttributeError as exc:
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with support.captured_stderr() as err:
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sys.__excepthook__(*sys.exc_info())
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self.assertIn("blech", err.getvalue())
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class ImportErrorTests(unittest.TestCase):
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def test_attributes(self):

‎Makefile.pre.in‎

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@@ -387,6 +387,7 @@ PYTHON_OBJS= \
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Python/dtoa.o \
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Python/formatter_unicode.o \
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Python/fileutils.o \
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Python/suggestions.o \
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Python/$(DYNLOADFILE) \
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$(LIBOBJS) \
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$(MACHDEP_OBJS) \

‎Misc/NEWS.d/next/Core and Builtins/2019-10-27-20-20-07.bpo-38530.ZyoDNn.rst‎

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@@ -0,0 +1,3 @@
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When printing :exc:`AttributeError`, :c:func:`PyErr_Display` will offer
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suggestions of simmilar attribute names in the object that the exception was
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raised from. Patch by Pablo Galindo

‎Objects/exceptions.c‎

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