On Thu, 15 May 2014 06:58:53 -0700, Rustom Mody wrote: > As far as I can see the votaries of the mystical 79 have yet to explain > how/where it appeared from
You're either trolling, or haven't been reading this thread in any detail. That's already been explained, repeatedly both in this thread and many times over the years: 79 is one less than 80, which is the standard width of many editors, which in turn comes from old dedicated terminals. Given your use of deliberately provocative terms like "votaries" and "mystical", I would say you're trolling. On the chance that you are asking an honest question, there's nothing "mystical" or magical about the number 79, or 80. 80 is a de facto standard. Had history turned out a bit different, that standard might have been 90 characters, or 70. Less likely (because people psychologically have a preference for multiples of ten over "random" numbers) it could have been 65, or 93, or any number somewhere in that range of 60 to 100 or thereabouts. But once a standard is established, even an arbitrary standard like 80 columns -- but not *entirely* arbitrary -- there is value in sticking to it *just because it is the standard*. There's nothing "mystical" about driving on the left hand side of the road (on the right hand side for Americans), but whatever choice everyone else has made, you really ought to do the same. Following the same standard simply makes interoperability easier and reduces friction. But as I said, 80 isn't *entirely* arbitrary. 8 characters would be too few; 800 would be too many. Approximately 60 to 100 characters or thereabouts is the "Goldilocks" zone of "not too few, not too many" for most texts. Think of it this way: every time the reader has to scroll horizontally, consider that as a page fault (it's an order of magnitude slower than scanning with the eyes). Every time a single logical expression has to be split over two lines, that's also a page fault. Every time you read a line of complicated code that does too much, that's also a page fault. We want to minimize the number of page faults. A limit of 60 characters would minimize the number of horizontal scrolling page faults (hardly anyone has their editor to display fewer than 60 characters!), but increase the number of expression-splitting page faults. A limit of 120 characters would reduce the number of expression-splitting page faults, but increase the number of horizontal- scrolling faults, and encourage people to write long lines of complicated code that does too much. Somewhere in between is a range that minimizes the number of page faults, hence maximizes readability. There's unlikely to be "One True Best Answer" to maximize readability at N characters, because maximum readability is dependent on the context. One can only hope to get close to maximum readability for a range of typical text, including code. That's likely to be around 80 characters, which fits nicely with the historical standard. Reducing that to 80-1=79 means you're protected from "off-by-one" errors in either your counting or your editor. -- Steven D'Aprano http://import-that.dreamwidth.org/ -- https://mail.python.org/mailman/listinfo/python-list
