__doc__ immutable for classes (was: Re: how to inherit docstrings?)
Eric Snow
ericsnowcurrently at gmail.com
Thu Jun 9 19:29:35 EDT 2011
On Thu, Jun 9, 2011 at 10:10 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
> Eric Snow wrote:
>>>> p.s. Am I missing something or can you really not change the docstring
>> of a class? I was thinking about the idea of inheriting class
>> docstrings too.
>> 8<--------------------------------------------------------
> """module level docstring"""
>> def func():
> """function level docstring"""
>> class Test(object):
> """class level docstring"""
> def meth(self):
> """method level docstring"""
>>> if __name__ == '__main__':
> import sys
> import traceback
> hmmm = (
> sys.modules['__main__'],
> func,
> Test(),
> Test().meth,
> Test,
> Test.meth,
> )
> for obj in hmmm:
> try:
> obj.__doc__ = 'new docstring'
> print('successfully changed %s\n' % obj)
> except:
> traceback.print_exc()
> print()
> 8<--------------------------------------------------------
>> Tested from 2.5 - 3.2. The first three always work, the last one works in
> 3.1+, the fourth and fifth always fail.
>> -----------------actual output for 2.5--------------------
> successfully changed <module '__main__' from 'docstring.py'>
>> successfully changed <function func at 0x00A8F570>
>> successfully changed <__main__.Test object at 0x00A94230>
>> Traceback (most recent call last):
> File "docstring.py", line 25, in <module>
> obj.__doc__ = 'new docstring'
> AttributeError: attribute '__doc__' of 'instancemethod' objects is not
> writable
> ()
> Traceback (most recent call last):
> File "docstring.py", line 25, in <module>
> obj.__doc__ = 'new docstring'
> AttributeError: attribute '__doc__' of 'type' objects is not writable
> ()
> Traceback (most recent call last):
> File "docstring.py", line 25, in <module>
> obj.__doc__ = 'new docstring'
> AttributeError: attribute '__doc__' of 'instancemethod' objects is not
> writable
> ()
> -----------------actual output for 3.2--------------------
> successfully changed <module '__main__' from 'docstring.py'>
>> successfully changed <function func at 0x00BE6F60>
>> successfully changed <__main__.Test object at 0x00BFE730>
>> Traceback (most recent call last):
> File "docstring.py", line 25, in <module>
> obj.__doc__ = 'new docstring'
> AttributeError: attribute '__doc__' of 'method' objects is not writable
>> Traceback (most recent call last):
> File "docstring.py", line 25, in <module>
> obj.__doc__ = 'new docstring'
> AttributeError: attribute '__doc__' of 'type' objects is not writable
>> successfully changed <function meth at 0x00BE6ED0>
> -----------------actual output----------------------------
>> ~Ethan~
>
Thanks for looking up all of that, Ethan! I would love to see __doc__
writable for classes. But for "method" objects (really a wrapper for
bound functions) would it change the __doc__ of the wrapper or of the
bound function? Seems like it is analogous to the Test().__doc__
case, so the wrapper would be updated. However, I haven't really had
a need to do that before, so I don't know which makes more sense.
Should I take this to python-ideas? And maybe Greg's thought of auto
inheriting __doc__?
-eric
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