On Thu, Oct 06, 2016 at 03:01:36PM +0100, Paul Moore wrote: > On 6 October 2016 at 14:45, Filipp Bakanov <fil...@bakanov.su> wrote: > > For now there are many usefull builtin functions like "any", "all", etc. I'd > > like to propose a new builtin function "equal". It should accept iterable, > > and return True if all items in iterable are the same or iterable is emty. > > That's quite popular problem, there is a discussion of how to perform it on > > stackoverflow > > (http://stackoverflow.com/questions/3844801/check-if-all-elements-in-a-list-are-identical) > > - all suggestions are either slow or not very elegant. > > What do you think about it? > > It's not a problem I've needed to solve often, if at all (in > real-world code). But even if we assume it is worth having as a > builtin, what would you propose as the implementation? The > stackoverflow discussion highlights a lot of approaches, all with > their own trade-offs. One problem with a builtin is that it would have > to work on all iterables, which is likely to preclude a number of the > faster solutions (which rely on the argument being an actual list). > > It's an interesting optimisation problem, and the discussion gives > some great insight into how to micro-optimise an operation like this, > but I'd question whether it needs to be a language/stdlib feature. > > Paul
I've needed it several times, but can't really remember what for anymore, which makes me think it's not really that important. A motivating reason for adding it to the builtins would be that it can be written in C instead of Python, and hence be a lot faster. The single slowest solution is actually the fastest when the difference is detected very soon (case s3), all others are `O(n)` and not `O(first-mismatch)`. Though, that means it could also be written in C and provided to PyPI, at the cost of asking others to install an extra package. _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
