John Machin wrote: > Fredrik Tolf wrote: > > I've been trying to get the string formatting operator (%) to work with > > more arguments than the format string requires, but I can find no way to > > do that. For example: > > > > >>> "%i" % 10 > > '10' > > >>> "i" % 10 > > Traceback (most recent call last): > > File "<stdin>", line 1, in ? > > TypeError: not all arguments converted during string formatting > > > > The thing is, I want to get format strings from the user, and I don't > > want to require the user to consume all the arguments. docs.python.org > > doesn't seem to have any clues on how to achieve this, and I can't think > > of what to google for. > > > > Could it be as I fear, that it is impossible? > > > > Three approaches spring to mind. In descending order of my preference: > > (a) don't do that > > (b) parse the format string, counting the number of args required. If > the user has supplied more, throw them away. > > (c) wrap your execution of format_string % args in a try/except > bracket. If you get a TypeError with that message [not guaranteed to > remain constant in the future], throw away the last arg and go around > again. > > As a matter of curiosity, why don't you want the user to consume all > the arguments? Don't they get even a teensy-weensy warning message? Are > you writing a Perl interpreter in Python? >
Another approach: instead of the "%s %.2f %.5f%%" style, give the users a list of names of each possible arg so that they can do e.g. "The rate for %(name)s is %(rate).5f%%" or "Amount borrowed: $%(amount).2f; borrower: %(name)s" HTH, John -- http://mail.python.org/mailman/listinfo/python-list
