[Python-Dev] Proposed PEP on concurrent programming support

[Jim Jewett]

(I've added back python-ideas, because I think that is still the
appropriate forum.)

>.... A new
> suite type - the ``transaction`` will be added to the language. The
> suite will have the semantics discussed above: modifying an object in
> the suite will trigger creation of a thread-local shallow copy to be
> used in the Transaction. Further modifications of the original will
> cause all existing copies to be discarded and the transaction to be
> restarted. ...

How will you know that an object has been modified?

The only ways I can think of are

(1)  Timestamp every object -- or at least every mutable object -- and
hope that everybody agrees on which modifications should count.

(2)  Make two copies of every object you're using in the suite; at the
end, compare one of them to both the original and the one you were
operating on.  With this solution, you can decide for youself what
counts as a modification, but it still isn't straightforward; I would
consider changing a value to be changing a dict, even though
nothing in the item (header) itself changed.

-jJ