On Thu, May 5, 2016, at 12:04 AM, Steven D'Aprano wrote: > On Thursday 05 May 2016 16:46, Stephen Hansen wrote: > > > On Wed, May 4, 2016, at 11:04 PM, Steven D'Aprano wrote: > >> Start by writing a function or a regex that will distinguish strings that > >> match your conditions from those that don't. A regex might be faster, but > >> here's a function version. > >> ... snip ... > > > > Yikes. I'm all for the idea that one shouldn't go to regex when Python's > > powerful string type can answer the problem more clearly, but this seems > > to go out of its way to do otherwise. > > > > I don't even care about faster: Its overly complicated. Sometimes a > > regular expression really is the clearest way to solve a problem. > > You're probably right, but I find it easier to reason about matching in > Python rather than the overly terse, cryptic regular expression mini- > language. > > I haven't tested my function version, but I'm 95% sure that it is > correct. > It trickiest part of it is the logic about splitting around ampersands. > And > I'll cheerfully admit that it isn't easy to extend to (say) "ampersand, > or > at signs". But your regex solution: > > r"^[A-Z\s&]+$" > > is much smaller and more compact, but *wrong*. For instance, your regex > wrongly accepts both "&&&&&" and " " as valid strings, and wrongly > rejects "ΔΣΘΛ". Your Greek customers will be sad...
Meh. You have a pedantic definition of wrong. Given the inputs, it produced right output. Very often that's enough. Perfect is the enemy of good, it's said. There's no situation where "&&&&&" and " " will exist in the given dataset, and recognizing that is important. You don't have to account for every bit of nonsense. If the OP needs a unicode-aware solution that redefines "A-Z" as perhaps "\w" with an isupper call. Its still far simpler then you're suggesting. -- Stephen Hansen m e @ i x o k a i . i o -- https://mail.python.org/mailman/listinfo/python-list
