[Python-ideas] Atomic counter / atomic increment

[Ben Hoyt]

> As long as Python uses a GIL to protect C level function
> calls, you can use an iterator for this:
>
> import itertools
> x = itertools.count()
> ...
> mycount = next(x)
>

Yeah, that's a neat hack -- I saw it recommended on StackOverflow, and saw
it used in the standard library somewhere. I think that's probably okay in
the *CPython* stdlib, because it's CPython so you know it has the GIL. But
this wouldn't work in other Python implementations, would it (IronPython
and Jython don't have a GIL). Or when itertools.count() is implemented in
pure Python on some system? Seems like it could blow up in someone's face
when they're least expecting it. I also think using *iter*tools is a pretty
non-obvious way to get a thread-safe counter.

-Ben
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