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Documenting a Python project

·4 mins

I’ve recently started contributing a little to GTG, a GTD-inspired todo list application that’s hosted on Launchpad.

So far, I’ve made a few UI tweaks and have done a bit of infrastructural work. I’m still trying to figure out how the code fits together. Since it’s such a small code base, I don’t mind writing a few docstrings for it. And if I’m going to write docstrings, I might as well generate some API docs, right?

And so the journey begins.

Everyone knows that pydoctor is the best way to generate API docs for Python code. So I fetched it from Launchpad and ran it according to the instructions:

$ bzr branch lp:pydoctor$ cd GTG$ ../pydoctor/bin/pydoctor --add-package GTG --make-html

This failed, saying it couldn’t find zope.interfaces. I know I have zope.interfaces on my system:

$ sagi python-zopeinterface...python-zopeinterface is already the newest version.

But, ah, this is karmic, and pydoctor is insisting on running with Python 2.4, which is completely broken on karmic. I tweaked the bin/pydoctor file to use the default Python and then ran the command again.

$ ~/src/pydoctor/trunk/bin/pydoctor --add-package GTG --make-html

Success, I think. There’s a lot of output, so it’s hard to tell. Trying again with a quiet option:

$ ~/src/pydoctor/trunk/bin/pydoctor --add-package GTG --make-html -qWARNING: guessing GTG for project name/home/jml/src/Divmod/trunk/Nevow/formless/ DeprecationWarning: object.__new__() takes no parametersrv = cls = InterfaceClass.__new__(cls, name, bases, dct)/home/jml/src/Divmod/trunk/Nevow/nevow/ DeprecationWarning: The popen2 module is deprecated.  Use the subprocess module.from popen2 import Popen3/home/jml/src/Divmod/trunk/Nevow/nevow/ DeprecationWarning: the md5 module is deprecated; use hashlib insteadimport md5these 6 objects' docstrings are not proper epytext:GTG.core.tagstore.Tag.__init__GTG.core.tagstore.Tag.set_attributeGTG.core.tagstore.Tag.get_all_attributesGTG.core.requester.Requester.new_taskGTG.core.requester.Requester.get_tasks_listGTG.core.requester.Requester.get_active_tasks_list

Hmm. The WARNING sucks, but I can work around that by specifying the project name on the command line. The deprecation warnings also suck, but I’m not quite sure what to do about them. For now, I’ll invoke python with ‘-W ignore::DeprecationWarning’.

This is as good a point as any to point out that I had Nevow trunk already in my PYTHONPATH. I don’t know what version of Nevow you will need.

The ’not proper epytext’ warnings are more worrisome. I thought I’d been writing proper docstrings. Also, it doesn’t tell me what the actual problems are: I need to drop the ‘-q’ option for that. This gets me too much information. Oh hello, there’s a ‘–verbose-about’ option. Digging into the source doesn’t enlighten immediately, but bzr-grep eventually reveals ‘–verbose-about=epydoc2stan2’. If I repeat ‘-q’ twice and the ‘–verbose-about’ option twice, I get precisely the output I want.

python -W ignore::DeprecationWarning ~/src/pydoctor/trunk/bin/pydoctor \--add-package GTG --make-html --project-name=GTG \-q -q \--verbose-about=epydoc2stan2 \--verbose-about=epydoc2stan2

What I really want is a pyflakes-style checker for my docstrings that I can hook up to flymake. That way, I can be warned about my poorly-formed docs as I’m writing them. Looking at the pydoctor help, it doesn’t look like such a thing exists. The command above is close, but it writes too much output to disk and takes far too long to run.

Also, it’s not quite right. It seems I’ve been writing my docstrings in the style we use in Launchpad, rather than in epytext style. So if I use ‘–docformat=restructuredtext’, my docstrings are formatted properly and I get fewer errors:

python -W ignore::DeprecationWarning ~/src/pydoctor/trunk/bin/pydoctor \--add-package GTG --make-html --project-name=GTG \--docformat=restructuredtext -q -q \--verbose-about=epydoc2stan2 --verbose-about=epydoc2stan2

This leaves only two formatting errors, both valid. It takes a full second longer to generate the docs, which sucks. Still, we’ve got doc generation, and we’ve got valid errors.

The output is good, but it’s not great. Take a look at the Twisted API docs, for example. I can’t quite put my finger on it, but I wish that someone with a vision and the kind of CSS skills that you have to buy from the devil at a crossroads at midnight would set themselves the task of making the API docs look great.

So where does this leave us:

  • I can generate pretty good API docs easily and get told only about interesting errors
  • I need a pyflakes-like docstring formatting checker
  • I need a simple docstring coverage checker. I do not want to make it part of my test suite or build process.
  • I had to tweak the pydoctor source before being able to run it from trunk
  • The output is OK, but it ought to be beautiful