[Python-3000] find -> index patch

[Michael Chermside]

Jack Diederich writes:
> I make a go at doing an idiomatic convertion [...] patch attached.
>
> WOW, I love partition.  In all the instances that weren't a simple "in"
> test I ended up using [r]partition.  In some cases one of the returned
> strings gets thrown away but in those cases it is guaranteed to be small.
> The new code is usually smaller than the old and generally clearer.

Wow. That's just beautiful. This has now convinced me that dumping
[r]find() (at least!) and pushing people toward using partition will
result in pain in the short term (of course), and beautiful, readable
code in the long term.

> If folks like the way this partial set looks I'll convert the rest.

Please do! Even if we *retain* [r]find(), this is still better code.
And I'm personally going to stop using [r]find() in my own code
starting today.

-- Michael Chermside