On Wed, Apr 25, 2018 at 3:19 AM, Steven D'Aprano <st...@pearwood.info> wrote: > On Wed, Apr 25, 2018 at 01:18:10AM +1000, Chris Angelico wrote: > >> First, though, can you enumerate (pun intended) the problems with >> magic strings? You list "no magic strings" as a benefit, as if it's >> self-evident; I'm not sure that it is. > > It shouldn't be self-evident, because the use of strings in the warnings > module doesn't match the most common accepted meaning of magic strings. > > https://en.wikipedia.org/wiki/Magic_string > > Possibly Jacco was thinking of "magic constants": > > https://en.wikipedia.org/wiki/Magic_number_%28programming%29#Unnamed_numerical_constants > > (although in this case, they're text constants, not numerical).
I assumed this to be the case, yes. Many people decry "magic numbers" where the number 7 means one thing, and the number 83 means something else; but I'm less convinced that the textual equivalent is as problematic. (If not "magic strings", what would you call them?) > A fairly lightweight change would be to add named constants to the > warning module: > > ERROR = 'error' > > etc, and refactor the module to use the named constants instead of > hard-coded strings. I'm surprised that it doesn't already do that. > > That would be 100% backwards compatible, without the cost of importing > and creating enums, but allow consumers of the warnings module to > inspect it and import symbolic names if they so choose: > > from warnings import ERROR Yeah, that would be one way to do it. But I'd still like to know what problems are being solved by this, as a means of determining whether they're being solved adequately. Is it the risk of misspellings? Because that can happen just as easily with the imported name as with a string literal. (The from-import pollutes your namespace, and "warnings.EROR" is a run-time failure just as much as a misspelled string literal would be.) Is it the need to list all the possible strings? That could be done with something like __future__.all_feature_names or the way the logging module translates level names into numbers. Something else? ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
