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copied!<p>Given your (unusual!) requirements, your implementation seems correct. In particular,</p> <ul> <li>If you're only updating one attribute, the Python GIL should be sufficient. Single bytecode instructions are atomic.</li> <li>If you do anything more complex, add locking! It's basically harmless anyway - if you cared about performance or multicore scalability, you probably wouldn't be using Python!</li> <li>In particular, be aware that <code>self.thing</code> and <code>self.n</code> in this code are updated in a separate bytecode instructions. The GIL could be released/acquired between, so you can't get a consistent view of the two of them unless you add locking. If you're not going to do that, I'd suggest removing <code>self.n</code> as it's an "attractive nuisance" (easily misused) or at least adding a comment/docstring with this caveat.</li> <li>Consumers don't need to make a copy. You're not ever mutating a particular object pointed to by <code>self.thing</code> (and couldn't with string objects; they're immutable) and Python is garbage-collected, so as long as a consumer grabbed a reference to it, it can keep accessing it without worrying too much about what other threads are doing. The worst that could happen is your program using a lot of memory from several generations of <code>self.thing</code> being kept alive.</li> </ul> <p>I'm a bit curious where your requirements came from. In particular, that you don't care if a <code>thing</code> is never used or used many times.</p>

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