On Sat, Jul 7, 2018 at 6:49 AM Marko Rauhamaa <ma...@pacujo.net> wrote: > Is that guaranteed to be thread-safe? The documentation (<URL: http > s://docs.python.org/3/library/stdtypes.html#dict.setdefault>) makes no > such promise.
It's guaranteed to be thread-safe because all of Python's core containers are thread safe (in as far as they document behaviors/invariants, which implicitly also hold in multithreaded code -- Python does not take the approach other languages do of "thread-compatible" containers that have undefined behavior if mutated from multiple threads simultaneously). It isn't guaranteed to be _atomic_ by the documentation, but I bet no Python implementation would make dict.setdefault non-atomic. There's no good description of the threading rules for Python data structures anywhere. ISTR there was a proposal to give Python some defined rules around thread-safety a couple of years ago (to help with things like GIL-less python projects), but I guess nothing ever came of it. -- Devin -- https://mail.python.org/mailman/listinfo/python-list
