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

Nick Coghlan ncoghlan at gmail.com
Sun Sep 14 15:03:20 CEST 2008

Georg Brandl wrote:

Nick Coghlan schrieb:

Armin Ronacher wrote:

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. list(iter) doesn't re-enter the eval loop if the iterator is written in C and hence won't let go of the GIL. As I believe the dict views in 3.0 are all C classes, I'd like to see a failing test case along these lines that doesn't involve a dict subclass and code written in Python. WeakKeyDictionary.keys() iterates over its .data dictionary's keys() instead of list(data.keys()). Therefore, the user of WeakKeyDictionary has no chance to do list(keys()) without running Python code.

Ouch, there's the dict subclass with Python code that I was asking for before I got concerned (I forgot that the weakref module is only partially implemented in C).

I agree this is a problem, but I'm struggling to think of possible solutions that aren't either horrendously complicated or completely contrary to the idea of view-based dicts.

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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