On Tue, Oct 20, 2020 at 10:37 PM Rob Cliffe via Python-ideas <python-ideas@python.org> wrote: > In short, "assigning" to f-strings is not and cannot be a simple reversal of > having them in expressions. Rather, it is opening a big can of worms. >
It's not a reversal of them being in expressions any more than assigning to a list display is a reversal of constructing a list. It's a parallel operation, a counterpart. It would be Python's way of offering an sscanf-like operation, which is something that I've frequently wished for. Regular expressions aren't ideal for all situations, and there are plenty of times when a simple set of parsing rules could be very nicely encoded into a compact form like this. C's sscanf and sprintf aren't perfect counterparts, but they're incredibly valuable. Python has percent formatting for sprintf, but no form of sscanf. > There is no precedent in Python for an expression on the LHS of an > assignment. (Tuple unpacking, dotted names, slices, dictionary keys etc. > might or might not be considered counter-examples but at least their intent > is clear.) Certainly not for something which looks like a literal on the LHS > of an assignment. > And the intent here would be just as clear. Assigning to a tuple or list has very well defined semantics, and they don't perfectly correspond to the way you would construct such a thing on the RHS. So, they *are* precedent for this. An sscanf format string is simple, easily understood, and unambiguous. An f-string assignment target would be the same, but using f-string style notation instead. It's that simple. ChrisA _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/2BFCFPDBV4OCTBOGV5UWKX6DJZKBEUUE/ Code of Conduct: http://python.org/psf/codeofconduct/
