[Python-Dev] Issue 14417: consequences of new dict runtime error (original) (raw)

Etienne Robillard animelovin at gmail.com
Thu Mar 29 23:03:17 CEST 2012

On 03/29/2012 04:48 PM, R. David Murray wrote:

On Thu, 29 Mar 2012 16:31:03 -0400, "R. David Murray"<rdmurray at bitdance.com> wrote:

On Thu, 29 Mar 2012 13:09:17 -0700, Guido van Rossum<guido at python.org> wrote:

My original assessment was that this only affects dicts whose keys have a user-implemented hash or eq implementation, and that the number of apps that use this and assume the threadsafe property would be pretty small. This is just intuition, I don't have hard facts. But I do want to stress that not all dict lookups automatically become thread-unsafe, only those that need to run user code as part of the key lookup.

You are probably correct, but the thing is that one still has to do the code audit to be sure...and then make sure that no one later introduces such an object type as a dict key. I just did a quick grep on our project. We are only defining eq and hash a couple places, but both are objects that could easily get used as dict keys (there is a good chance that's why those methods are defined) accessed by more than one thread. I haven't done the audit to find out :) The libraries we depend on have many more definitions of eq and hash, and we'd have to check them too. (Including SQLAlchemy, and I wouldn't want that job.) So our intuition that this is not common may be wrong. --David

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Hm, as far I understand this seems like an issue for gnu PTH, not python job, which should transparently handles thread safety issues based on the host/machine capabilities. Therefore I hope the fix in python don't affect thread-unsafe apps to raise spurious RuntimeErrors when a dict get modified across a SMP-aware platform... :-)

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