[Python-ideas] Atomic counter / atomic increment

[M.-A. Lemburg]

On 25.08.2016 19:31, Ben Hoyt wrote:
> I had to implement a simple atomic counter the other day to count the total
> number of requests processed in a multi-threaded Python web server.
> 
> I was doing a demo of "how cool Python is" to my colleagues, and they were
> generally wowed, but one of the things that made them do a double-take
> (coming mostly from Scala/Java) was that there was no atomic counter in the
> standard library.
> 
> The fact that I and many other folks have implemented such things makes me
> wonder if it should be in the standard library.

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)
...

The trick here is that the CALL_FUNCTION byte code will trigger
the increment of the iterator. Since this is implemented in C,
the GIL will serve as lock on the iterator while it is
being incremented.

With Python 4.0, this will all be different, though :-)

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