switch recipe?

[Tim Peters]

[Tim]
> So my candidate for simplification is:
>
> def make_switch(*args):
>     """Generate the elements in args repeatedly."""
>     if not args:
>         raise TypeError("at least one argument required")
>     while True:
>         for a in args:
>             yield a
>
> I'd lose the "if not args:" block, though; if the arglist is
> empty, it will simply terminate without yielding anything, and that's
> what I expect the empty case to do.

[Mark McEahern]
> If you leave the while True, then it won't raise StopIteration
> when you call it without arguments.

So true -- and even if you change it to "while 1" <wink>.

> The simple fix is to replace that with while args.

Yes, that's nice!

> Here's the result of my latest tinkering.  For what it's worth, I think I
> prefer raising the error in the generator when args is not specified
> rather than waiting until next() is called the first time--on the
> principle that raising the error earlier is better.

Then that's where we differ:  I don't consider an empty sequence to be "an
error" in any sense of the word.  For the same reason, range(10, 10) doesn't
complain in Python, or string[i:i], etc -- doing nothing gracefully is
important because there's sometimes nothing that needs be done <wink>.