[Python-Dev] Weak Dictionary Iteration Behavior in Python 3 (original) (raw)

Armin Ronacher armin.ronacher at active-4.com
Sun Sep 14 11:39:31 CEST 2008

Hi,

Adam Olsen <rhamph gmail.com> writes:

IMO, this is a deeper problem than suggested. As far as I know, python does not (and should not) make promises as to when it'll collect object. We should expect weakrefs to be cleared at random points, and code defensively. It doesn't promise when objects are collected and that's not the problem here. The main problem is that the old solution for weakrefs relayed on the fact that .keys() was considered atomic. I don't say it has to become again, but the weak dictionaries have to somehow counter that problem. They could for example only remove items from the internal dict if no dict view to that dict is alive.

Speaking of atom keys() / values() / items() operations: I guess we will see more of those problems in threaded situations when people start to convert code over to Python. I've seen quite a few situations where code relays on keys() holding the interpreter lock.

Regards, Armin

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