On Thu, Jul 09, 2020 at 10:25:46PM +1000, Chris Angelico wrote:
Getting a random element from a dict (not an arbitrary one but a random one) definitely does have a use-case. I've wanted it at times. Usually if I'm doing this in Python, I just pay the price and build the list, but as proof that it's a logical and useful operation, here's Pike's general random function:
http://pike.lysator.liu.se/generated/manual/modref/ex/predef_3A_3A/random.ht...
If given a number, it picks a random number. If given an array, it picks a random element. And if given a mapping (dictionary), it returns (key,value), without first converting to a flat list.
That's an existance proof that somebody else implemented the function, not a use-case. Getting a random key/item pair directly from a dict is a mechanism, not an explanation of why you need a random key-item pair. Analogy: "Intercal's random function accepts a module as argument and returns the value of a random global variable from that module." (In real life it doesn't, so far as I know, but it should. If not Intercal, perhaps Malbolge, or another such escoteric language designed to be impractical and frustrating.) I'll admit that I can't actually think of a reason why one should not want a random key/value pair, but that's not the same as being able to think of a reason why one *would* want a random key/value pair. Perhaps I just lack imagination. But as you say:
I don't think the use-case is strong enough, since there are many possible variants you might want (imagine using collections.Counter to define a weighted average - it'd be handy to say "pick a random element, treating this as a bag/multiset"), so it's best to just custom write it when you need it.
-- Steven