On Fri, Nov 21, 2014 at 4:42 AM, <random...@fastmail.us> wrote: > On Thu, Nov 20, 2014, at 09:59, Chris Angelico wrote: >> >> Why should it encode to bytes? > > Because a bytes format string suggests a bytes result. Why does unicode > always "win", rather than the type of the format string always winning?
For the same reason that float always "wins": >>> 1.0 + 2 3.0 >>> 1 + 2.0 3.0 >> Makes much better sense to work in >> Unicode. But mainly, it has to do one of them, and be predictable. > > Yeah, but string % is not a symmetrical operator. People's mental model > of it is likely to be that it acts like format (which does use the type > of the format string) or C sprintf/wsprintf (both of which use the same > type for the format string and result). And literally every other type > is converted to the type of the format string when used with %s - having > unicode be special adds cognitive load, and it means you can't safely > blindly use %s with an unknown object. True, but Python 2 deliberately lets you conflate the two, so you get a bit of convenience at the expensive of complexity when things go wrong. Python 3, on the other hand, is much more careful about the difference: >>> "asdf %s qwer" % b"zxcv" "asdf b'zxcv' qwer" >>> b"asdf %s qwer" % "zxcv" Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for %: 'bytes' and 'str' So your complaint *has* been resolved... but only in Python 3, because the change would break stuff. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
