[Python-Dev] Sharing docstrings between the Python and C implementations of a module (original) (raw)

David Lam david.k.lam1 at gmail.com
Mon Apr 15 09:56:07 CEST 2013

Recently I helped out on issue16954 which involved filling in docstrings for methods and classes in ElementTree.py

While doing so, I tried to test my work in the interpreter like this...

>>> from xml.etree.ElementTree import Element
>>> help(Element)

...but found that help() showed nothing but empty strings!

After some debugging, I found that the culprit was the from _elementtree import * near the bottom of the module.

Not wanting to copy & paste docstrings around, I thought one solution might be to just reassign Element.doc with the right docstring. But, it seems that you can't do that for C extensions:

>>> from _elementtree import Element as cElement
>>> cElement.__doc__ = 'correct docstring'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't set attributes of built-in/extension type

'xml.etree.ElementTree.Element'

Q. Is there way to maintain the same docstring without resorting to copying and pasting it in two places?

I tried to find an example in the source which addressed this, but found that the docstrings in similar cases to be largely duplicated. For instance, datetimemodule.c, decimal.c and _json.c all seem to exhibit this docstring copy and pastage. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20130415/67f2843e/attachment.html>

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