Moderate Realism

You’ve probably seen the mailing list announcements and the tweets which declare that Python 3.3 is entering its beta stage. For core developers this means that no more features can be introduced into this version of Python (at least not without the connivance of the Release Manager: Georg Brandl). Bug fixes are still allowed — which sometimes leads to rather creative labelling of changesets.

Have a look at the preliminary “What’s New?” doc.

Up to now, Python core developers have been championing Python 3 over Python 2 largely on the basis of a significant amount of cleanups, rationalisation and cruft-clearing. Now all this is very good, but mostly pleases people who have to work with the underlying Python code & data or who are fond of housekeeping. Clearly there have been other additions. (In fact the more I read through the “What’s New?” documents the more I realise that we’ve been doing something of a poor job of advertising our own achievements). But there hasn’t perhaps been anything which is really structurally groundbreaking.

Now we’ve got built-in virtual environment support, proper namespace packages, a much clearer OS exceptions hierarchy, and — at long last — a way of yielding from other iterators. (That thing where you had to loop over an iterator yielding its values: you can now just “yield from”). Any one of those alone is surely worth the entrance price. It’s actually starting to become attractive to use Python 3.x not just because it’s cleaned-up (on the moral highground but without much of a change of scenery) but because it’s got cool new features that I actually need (wow! look at that view).

To be sure there are literally hundreds of other small changes, ranging from one-off bugfixes to large-scale rewrites: bz2 has been rewritten from scratch; Brett Cannon’s finally achieved his objective of reimplementing the import mechanism in Python; Unicode support under the covers is cleaner and faster; the useful-but-slower decimal module is now useful-but-faster thanks to a version written in C, the indefatigable Stefan Krah getting the credit there. And after much bouncing around, Peter Moody’s ipaddress module is now integrated in the stdlib.

For Windows users, two significant changes have made it in (although they haven’t reached the What’s New? docs yet). One is the implementation of PEP 397 — a Python launcher for Windows, conceived by Mark Hammond, with implementation work by Vinay Sajip and worked up into its final form by Martin von Loewis. The other, implemented by Brian Curtin, is the addition of python.exe to the system PATH. This one is a long-standing gripe especially for novice users who can now just type “python” at the command prompt and get the latest version up. In fact, the PEP 397 launcher makes this perhaps less important but it’s still good to have the option there in the installer.

I’m trying to help along a couple of changes to the Win32 implementation of some os pieces under the guise of bugfixes, but even if I don’t get them past the eagle eye of the release manager, this’ll still be a version to look forward to.

Thanks to everyone who commented on my previous PEP8-related posts. It’s been quite an eye-opener for me to see how many people felt strongly that PEP8-compliance was a real must-have, not just for core Python itself but for any Python project. My own use of Python just about predates PEP8 itself, and certainly predates its more widespread adoption within the community. And, while I was aware that it was a default recommendation for someone seeking style guidelines, I don’t think I’d appreciated just how wide and strong its uptake was.

Of the comments made to my previous posts, only one outright dismissed PEP8; several spoke neutrally, more or less echoing the sentiments I’d expressed; but the majority which expressed a clear opinion made it strongly advisable, not to say mandatory, to follow PEP8 for one’s own (published) work.

So I’ve decided to switch to near-PEP8 style. (Note that pretty much everyone and every project varies a little, most commonly on the line length issue). The two key points which seemed — startlingly, from my perspective — to bother people the most were the two-space indents and the space-before-brackets. If you cared to peruse my winshell & active_directory github repos, you’ll note that those are now in line with PEP8. Others will follow as and when.

You’re probably not surprised to hear me say that, having made the switch, I can’t understand how anyone can prefer the PEP8 style. If I’ve switched, it’s not because I’ve had a sudden aesthetic revelation which makes me wonder why I wasn’t using 4-space indents all along. Quite the reverse: for the life of me I can’t see why anyone would prefer it. Rather, it’s because I recognise the value of a commonly-held standard within a community. And because, when I weighed it up, there was no reason — beyond my own preferences — not to switch.

I’ve tweaked my SciTE options and added the PEP8 module to my test scripts, turning off certain of the checks and allowing for slightly longer lines. Let’s see what I feel about this in a month or so’s time.

Well I certainly got some robust comments on my previous PEP8 post. A few people chimed on my side, so to speak. Someone else found it “discouraging” when faced with “non-compliant code”. But it was Luke who obviously felt most strongly about the matter, and it’s his points that I’m really addressing here.

First of all, it seems that you’ve got me coming and going: on the one hand, I’m unreasonable to expect people to adopt my project’s style when contributing to it; but on the other I’m unreasonable if I expect to program the same way in every environment. Let me say again what I said in the previous post: if I contribute to, say, core Python, then I *do* expect to have to change my style to match the project guidelines. Likewise, if I contribute to Pyro — a fairly well-known Python project — then I use camelCase method names, because that’s what its maintainer uses. I don’t find that so very difficult and I doubt it anyone else does either. (Of course my “anyone else does” here is as anecdotal as the generalisations in Luke’s comments and can be treated the same way).

Luke’s basic point seems to be that all Python code *should* look the same, regardless of any other consideration, and that to do otherwise is not to be a team player, to indicate that you don’t care, and to leave open the suspicion that your code is of as poor quality as… well, your PEP8-ness. And I find that position far beyond what I consider reasonable. If that leaves me turning people away at the door then please write and tell me. Perhaps I’m being a single-minded curmudgeon on this issue, but I am honestly bemused at the idea that *all* Python code should follow what is, basically, one person’s preferences.

In short, I would be genuinely interested to hear from other people if they think that publishing Python code which follows a consistent style but which is not PEP8-compliant is that much of an issue. For them, for would-be contributors, or for the image of Python.

From time to time someone comments on some code example I’ve produced (or, indeed, one of my published modules) and makes the point that the code is not PEP8-compliant. The most common complaints are that I use spaces before function-call brackets — spam (”foo”) rather than spam(”foo”) — and that I use 2-space indents rather than 4.

Since I’ve written pretty much the same answer whenever this has been raised, I thought I might as well write it here and then point people towards it.

PEP 8 is the Python project’s code style guideline. I quote from the opening paragraph: “This document gives coding conventions for the Python code comprising the standard library in the main Python distribution.”. It is not a guideline for every piece of Python code ever written by anyone. On the odd occasion that I contribute code to the Python core I naturally ensure that my code complies with PEPs 7 & 8 for C & Python code respectively.

I’ve been using the format described above for well over 25 years of coding on different platforms & languages. Along with other aspects, it constitutes my personal “house style”. If anyone wished to contribute to any of my projects I would ask them to follow the same guidelines (or at least, not to complain when I reformatted their code to match my own).

FWIW I find the spam(”foo”) style cramped; no doubt some people find my spam (”foo”) style too loose. So be it. I’m genuinely astonished when people advocate 8-space indents (and I’d be a bit startled by 1-space indents). I find 4 spaces push the relevant code too far away too easily so I use 2 spaces. Barring manifest absurdities, such things are largely subjective.

So now you know: if you see code examples of mine, or are perusing my source code, be prepared for (gasp) non-PEP8 compliance!

In a fit of energy over the weekend, I added some basic Recycle Bin functionality to the winshell module. (And thanks to Steve Reiss for the suggestion and for ideas about convenience functions). As of version 0.6.1 you can now:

• Iterate over items in the recycle bin
• Determine what versions of a file there are in the recycle bin
• Undelete the latest or a specific version of a file
• Empty all recycle bins

You could already delete to the Recycle Bin (via delete_file). Now you can undelete as well!

• pip install winshell
• github: http://github.com/tjguk/winshell
• PyPI: http://pypi.python.org/pypi/winshell
• readthedocs.org: http://readthedocs.org/docs/winshell/