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Add details for pickle serialization errors #122213
Description
Feature or enhancement
When pickling a complex object, or a graph of objects, it is difficult to locate the source of error. At best you get the type of the unpickleable object at the bottom level, but you cannot know the part of what object or data structure it is.
The proposed PR adds notes to the raised exception which allow to identify the source of the error. For example:
>>> import pickle
>>> pickle.dumps([{'a': 1, 'b': 2}, {'a': 3, 'b': pickle}])
Traceback (most recent call last):
File "<python-input-1>", line 1, in <module>
pickle.dumps([{'a': 1, 'b': 2}, {'a': 3, 'b': pickle}])
~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: cannot pickle 'module' object
when serializing dict item 'b'
when serializing list item 1>>> class A: pass
...
>>> a = A()
>>> a.x = pickle
>>> pickle.dumps(a)
Traceback (most recent call last):
File "<python-input-5>", line 1, in <module>
pickle.dumps(a)
~~~~~~~~~~~~^^^
TypeError: cannot pickle 'module' object
when serializing dict item 'x'
when serializing A stateSee also similar issue #122163 for JSON.
Activity
pythongh-122213: Add notes for pickle serialization errors
gh-122213: Add notes for pickle serialization errors (GH-122214)
pythongh-122213: Add notes for pickle serialization errors (pythonGH-…
[3.12] pythongh-122213: Add notes for pickle errors