On Dec 20, 8:49 pm, MRAB <goo...@mrabarnett.plus.com> wrote: > Aaron Brady wrote: > > On Dec 20, 7:38 pm, Steven D'Aprano <st...@remove-this- > > cybersource.com.au> wrote: > >> Instead of just whinging, how about making a suggestion to fix it? Go on, > >> sit down for an hour or ten and try to work out how a BINARY OPERATOR > >> like % (that means it can only take TWO arguments) can deal with an > >> arbitrary number of arguments, *without* having any special cases. > > >> Go on. Take your time. I'll be waiting. > > > Hi, not to take sides, but, there is a possibility. > > > This behavior is currently legal: > > >>>> "%i %%i" % 0 % 1 > > '0 1' > > > So, just extend it. (Unproduced.) > > >>>> "%i %i" % 0 % 1 > > '0 1' > >>>> "%r %i" % (2, 3, 4) % 1 > > '(2, 3, 4) 1' > >>>> "%r %i" % (2, 3, 4) > > '(2, 3, 4) %i' > > > Which is quite clever and way ahead of its (posessive) time. > > A couple of problems: > > 1. How do you handle a literal '%'? If you just double up then you'll > need to fix the string after all your substitutions. > > 2. What if a substitution introduces a '%'? > > I suppose a possible solution would be to introduce a special format > string, including a literal, eg: > > f"%r %i" % (2, 3, 4) % 1 > > and then convert the result to a true string: > > print(str(f"%r %i" % (2, 3, 4) % 1)) > > (although print() would call __str__ anyway). > > The format string would track where the last substitution occurred. > > Hmm... I think I'll just learn the new method. :-)
Now that I'm fighting 'r's war for him/her... Um, here's one possibility. On the first interpolation, flags are noted and stored apart from subsequent interpolations. Then, use a sentinel to terminate the interpolation. (Unproduced.) >>> "%r %i" % ( 2, 3 ) % 0 '(2, 3) 0' >>> "%% %r" % ( 2, 3 ) % str.interp_end '% (2, 3)' >>> "%sss%i" % "%d" % 0 '%dss0' The first %s is replaced with %d, but doesn't hijack the '0'. If you want to interpolate the %d, use the sentinel. The sentinel is what causes '%%' to be handled. >>> "%sss%i" % "%d" % 0 % 1 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: not all arguments converted during string formatting >>> "%sss%i" % "%d" % 0 % str.interp_end % 1 '1ss0' Treating tuples as a special case appears to be the simpler solution, but this, 'chaining', to adopt the term, is still feasible. -- http://mail.python.org/mailman/listinfo/python-list
