On Tue, Sep 6, 2016 at 3:04 PM, Tim Peters <tim.pet...@gmail.com> wrote:
> But would you _use_ it? I'm still asking for use cases. > > When, e.g., I'm randomizing permutations for testing, the last thing I > want is: > > while whatever: > result = function_of_xs(shuffled(xs)) > check result and complain if it's wrong > > Why not? Because no trace remains of _which_ permutation provoked the > failure when a failure occurs. Instead code looks like this: > > while whatever: > shuffle(xs) > result = function_of_xs(xs) # or xs[:] if the function mutates > its arg > check result and complain that `xs` specifically provoked a failure > > Indeed, the only clear "use case" that makes sense I've been able to > think of is: > > xs = shuffled(xs) > > But that's written more easily and efficiently today as > > shuffle(xs) > > This is in stark contrast to sorted(), where clear use cases abound. > That didn't get in because it's hard to mimic (it's basically as easy > as shuffled()), but because it's exactly what's wanted in all kinds of > contexts in all kinds of code. > I'll weigh in and say that I've had a few cases where I've wanted a shuffled function, but not many. The vast majority are interactive uses, where I want to get a sampling of data, and in those cases I'm normally just printing the output (often, by letting the REPL handle it). I'm fairly sure I've never wanted a shuffled in the actual code, and shuffle is almost always what I want (or just pulling items at random). Probably the most common case is to produce a list of random numbers in a (small) range. The current code looks roughly like: import random items = list(range(10)) random.shuffle(items) items # this is interactive, so this prints it for me As this does not come up often, I almost invariably write the following first: import random random.shuffle(range(10)) Then get no output and write the first form. It is not a major difference, and only comes up maybe a few times a year at most for me. Chris
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