On Jun 21, 2009, at 5:40 PM, Eric Smith wrote:
I've basically come to accept that %-formatting can never go away, unfortunately. There are too many places where %-formatting is used, for example in logging Formatters. %-formatting either has to exist or it has to be emulated.
It'd possibly be helpful if there were builtin objects which forced the format style to be either newstyle or oldstyle, independent of whether % or format was called on it. E.g. x = newstyle_formatstr("{} {} {}") x % (1,2,3) == x.format(1,2,3) == "1 2 3" and perhaps, for symmetry: y = oldstyle_formatstr("%s %s %s") y.format(1,2,3) == x % (1,2,3) == "1 2 3" This allows the format string "style" decision is to be made external to the API actually calling the formatting function. Thus, it need not matter as much whether the logging API uses % or .format() internally -- that only affects the *default* behavior when a bare string is passed in. This could allow for a controlled staged towards the new format string format, with a long deprecation period for users to migrate: 1) introduce the above feature, and recommend in docs that people only ever use new-style format strings, wrapping the string in newstyle_formatstr() when necessary for passing to an API which uses % internally. 2) A long time later...deprecate str.__mod__; don't deprecate newstyle_formatstr.__mod__. 3) A while after that (maybe), remove str.__mod__ and replace all calls in Python to % (used as a formatting operator) with .format() so that the default is to use newstyle format strings for all APIs from then on. James