Exactly this!

Yup! It's called Hash flooding / HashDoS (en.wikipedia.org/wiki/Collisi...)

They can collide due to the pigeon hole principle of course.

True - but why does it have to be random? There's a cool reason ;)

Agreed! Also, the reason why the effective order is different in every run is pretty interesting ;)

Ah, but this isn't just about the order - it's about why it's non-deterministic! There's an interesting story and reason behind that :)

Yup. To be more exact, cPython's compiler does constant deduplication inside a compilation unit (i.e. a single "code" object). If it compiles lines separately like in normal REPL use, it won't deduplicate 257. If it would compile them at the same time (like in that py file), they get deduplicated.

Source: a question asked by an attentive attendee at my Python workshop yesterday.

Thanks! That's MacOS Terminal.app, right?