On Sat, Feb 22, 2014 at 12:53 AM, Nick Coghlan <ncogh...@gmail.com> wrote: > On 21 February 2014 22:42, Chris Angelico <ros...@gmail.com> wrote: >> People can already write: >> >> if (x if y else z): >> >> without the parens, and it works. Readability suffers when the same >> keyword is used twice (here "if" rather than the colon, but same >> difference), yet the parens are considered optional. Python is a >> language that, by and large, lacks syntactic salt; style guides are >> free to stipulate more, but the language doesn't make demands. I would >> strongly *recommend* using parens in all the cases you've shown, >> especially lambda: >> >>> lambda x: calculate(x) except Exception: None >>> lambda x: (calculate(x) except Exception: None) >> >> as it would otherwise depend on operator precedence; but mandating >> them feels to me like demanding readability. > > Right, that's why my main motivation for this suggestion is the one > relating to keeping future options open. If the parentheses are > optional, than adding multiple except clauses latter isn't possible, > since this would already be valid, but mean something different: > > expr except Exception1: default1 except Exception2: default2 > > The deferral currently has this snippet: > > """In order to ensure compatibility with future versions, ensure that > any consecutive except operators are parenthesized to guarantee the > interpretation you expect.""" > > That's not a reasonable expectation - either the parentheses have to > be mandatory as part of the deferral, or else multiple except clause > support needs to be listed as rejected rather than deferred.
I've spent the better part of the last hour debating this in my head. It's basically a question of simplicity versus future flexibility: either keep the syntax clean and deny the multiple-except-clause option, or mandate the parens and permit it. The first option has, in my own head, the stronger case - this is designed for simplicity, and it wouldn't be that big a deal to completely reject multiple except clauses and simply require that the _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
