On Fri, 8 May 2020 23:10:05 +1000 Steven D'Aprano <st...@pearwood.info> wrote:
> On Thu, May 07, 2020 at 03:43:23PM +0200, Dominik Vilsmeier wrote: > > How common is it to compare two objects where you cannot determine > > whether one or the other is a tuple or a list already from the > > surrounding context? In the end these objects must come from somewhere > > and usually functions declare either list or tuple as their return type. > Never, because we can always determine whether something is a list or > tuple by inspecting it with type() or isinstance(). But that's missing > the point! I don't care and don't want to know if it is a tuple or > list, I only care if it quacks like a sequence of some kind. > The use-case for this is for when you want to compare elements without > regard to the type of the container they are in. This is a duck-typing > sequence element-by-element equality test. To rephrase Dominik's question slighly, how often do you have a block of code with two sequences of unknown origin? Sure, I can *hypothisize* f(x, y) where x and y don't have to be anything more specific than sequences. But unless I'm actually writing .EQ., there's some code inside f that builds x or y, or calls some other function to obtain x or y, and then I know at least one of the types. You often ask for real world code that would be simpler or easier to read or maintain if such-and-such feature existed. The OP never posted any such thing; do you have any specific code in mind? > If you have ever written something like any of these: > > list(a) == list(b) > tuple(a) == b > ''.join(chars) == mystring > all(x==y for x,y in zip(a, b)) > > then this proposed operator might be just what you need. Ever? Maybe. Do I need help from a new operator or the standard library when it comes up? No, not really. And except for that join/mystring example, I find all of thse examples incredibly obvious and simple to read (although looking up a new function or operator isn't onerous, and I often learn things when that happens). -- “Atoms are not things.” – Werner Heisenberg Dan Sommers, http://www.tombstonezero.net/dan _______________________________________________ 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/PU2GE3BVZOAAW7DRFWBRYUHHX6RII3MP/ Code of Conduct: http://python.org/psf/codeofconduct/
