Wrong behavior of help function on module #77849

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1. OlegOleinik commented on May 28, 2018

   

   OlegOleinikmannequin

   on May 28, 2018

   MannequinAuthor

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   I write file test.py:
   def __getattr__(key):
   return None
   help(name)

   when I try to run it I've got error:
   Traceback (most recent call last):
     File "test.py", line 5, in <module>
       help(__name__)
     File "C:\Program Files\Python37\lib\_sitebuiltins.py", line 103, in __call__
       return pydoc.help(*args, **kwds)
     File "C:\Program Files\Python37\lib\pydoc.py", line 1894, in __call__
       self.help(request)
     File "C:\Program Files\Python37\lib\pydoc.py", line 1944, in help
       elif request: doc(request, 'Help on %s:', output=self._output)
     File "C:\Program Files\Python37\lib\pydoc.py", line 1674, in doc
       pager(render_doc(thing, title, forceload))
     File "C:\Program Files\Python37\lib\pydoc.py", line 1667, in render_doc
       return title % desc + '\n\n' + renderer.document(object, name)
     File "C:\Program Files\Python37\lib\pydoc.py", line 385, in document
       if inspect.ismodule(object): return self.docmodule(*args)
     File "C:\Program Files\Python37\lib\pydoc.py", line 1136, in docmodule
       for key, value in inspect.getmembers(object, inspect.isclass):
     File "C:\Program Files\Python37\lib\inspect.py", line 330, in getmembers
       for base in object.__bases__:
   TypeError: 'NoneType' object is not iterable

   If I change definition of __getattr__ function to:
   def __getattr__(key):
   raise AttributeError()
   then help function runs without errors. But I need to return None value from __getattr__ function.
   When I wrote this function in class definition there is also no errors during runtime
2. OlegOleinik

   added

   3.7 (EOL)end of lifeend of life

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 28, 2018
3. ilevkivskyi commented on May 31, 2018

   

   ilevkivskyi

   on May 31, 2018

   Member

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   Hm, replacing the return with a random string, this leads to another crash:

   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/Users/ilevkivskyi/src/cpython/Lib/_sitebuiltins.py", line 103, in __call__
       return pydoc.help(*args, **kwds)
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 1895, in __call__
       self.help(request)
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 1954, in help
       else: doc(request, 'Help on %s:', output=self._output)
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 1674, in doc
       pager(render_doc(thing, title, forceload))
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 1667, in render_doc
       return title % desc + '\n\n' + renderer.document(object, name)
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 385, in document
       if inspect.ismodule(object): return self.docmodule(*args)
     File "/Users/ilevkivskyi/src/cpython/Lib/pydoc.py", line 1157, in docmodule
       for importer, modname, ispkg in pkgutil.iter_modules(object.__path__):
     File "/Users/ilevkivskyi/src/cpython/Lib/pkgutil.py", line 123, in iter_modules
       raise ValueError("path must be None or list of paths to look for "
   ValueError: path must be None or list of paths to look for modules in

   The reason is that __getattr__ is also triggered when a special attribute is looked up. I am not sure what to do with this. This is a bit inconsistent with how classes behave, where e.g. __len__ is never searched on an instance. But modules are special in many other ways, so maybe we can just fix pydoc (and other tools like inspect) to expect some ill-typed values in special module attributes and fail gracefully?
4. ilevkivskyi commented on May 31, 2018

   

   ilevkivskyi

   on May 31, 2018

   Member

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   Adding Yury as an inspect expert. I don't think this is something urgent, we can probably postpone this to 3.7.1.
5. corona10 commented on Jul 14, 2018

   

   corona10

   on Jul 14, 2018

   Member

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   This script works well on Python2 but not on Python3.
   I've submitted a PR. Please take a look.
6. corona10 commented on Jul 14, 2018

   

   corona10

   on Jul 14, 2018

   Member

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   I've checked both cases are now working on my patch.
7. corona10 commented on Aug 1, 2019

   

   corona10

   on Aug 1, 2019

   Member

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   I close PR 8284.

   If there is a chance to work with this issue.
   Please let me know

   Thanks!
8. ezio-melotti

   transferred this issue fromon Apr 10, 2022