Thread-safety of dict

Duncan Booth duncan.booth at invalid.invalid
Fri Jun 1 11:51:13 CEST 2007

"Adam Olsen" <rhamph at> wrote:

> So there you have it: if you're using a dict with custom classes (or
> anything other than str) across multiple threads, and without locking
> it, it's possible (though presumably extremely rare) for a lookup to
> fail even through the key was there the entire time.

Nice work.

It would be an interesting exercise to demonstrate this in practice, and I 
think it should be possible without resorting to threads (by putting 
something to simulate what the other thread would do into the __cmp__ 

I don't understand your reasoning which says it cannot stay in 
ma_smalltable: PyDict_SetItem only calls dictresize when at least 2/3 of 
the slots are filled. You can have 5 items in the small (8 slot) table and 
the dictionary will resize to 32 slots on adding the 6th,the next resize 
comes when you add the 22nd item.

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