[Python-ideas] Shuffled

[Steven D'Aprano]

On Thu, Sep 08, 2016 at 12:22:28AM +0200, Sven R. Kunze wrote:

> About the confusion of returning None. It's not confusing in the sense 
> of "o my god, I did it wrong, I need to learn it", but more, like "I 
> used shuffle, BECAUSE it's the only one I could find in a hurry"

Then don't be in such a hurry.

Honestly, there is no substitute for professionalism. Outside of fantasy 
novels and movies, there has never been a "ticking time bomb" situation 
where a programmer has to write code to shuffle a list in six seconds or 
the world will be destroyed. There is *always* time to at least glance 
at the docs, and it is never more than a handful of keypresses away in 
the interactive interpreter:

    help(random.shuffle)

And if you don't read the docs? Oh well, you find out soon enough once 
you actually test your code or have a code review. No harm done.

If the programmer doesn't do *any* of those things -- doesn't read the 
docs, doesn't test their code, doesn't do code reviews -- then there's 
no hope for them. We could provide shuffled() and shuffle() and they'll 
still end up picking the wrong one fifty percent of the time.

"My wild guess of how a function works was wrong, so now I'm cheesed off 
that the function doesn't do what I expect" is NOT a good reason to add 
things to the standard library.

> I would expect this from 
> Python as it already provides both alternatives for sorting".

Does that mean you expect Python to provide appended() as well as 
append(), extended() as well as extend(), popped() as well as pop(), 
cleared() as well as clear(), inserted() as well as insert(), removed() 
as well as remove()?

If your response is to say "Why do we need all those? Why on earth would 
anyone need to use list.cleared()?" then perhaps you can now understand 
why shuffled() has to prove itself too. Functions don't get added just 
because they *can* be added. They have to be worth it. Every function 
has costs as well as benefits. Each function adds:

- more code to download, compile, maintain
- more tests
- more documentation
- more for the user to learn
- more choices for the user to decide between
- more complexity
- more risk of bugs

Unless the proposal can demonstrate that the benefit outweighs the 
costs, it should not be added. Merely stating that you need it 
doesn't demonstate that a four-line helper function at the top of 
your module isn't sufficient.

For what's it is worth, if it were *my* call, I'd accept that the costs 
of adding this are low, but the benefits are just a *tiny* bit higher. 
But that's a judgement call, and if Raymond see the cost:benefit ratio 
going the other way, I have no objective argument to change his mind.



-- 
Steve