Python 3.4 is one of the most feature-packed releases I recall. Besides the obvious new perks like enums and asyncio, note some hidden gems like PEP 442:
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This PEP removes the current limitations and quirks of object finalization. With it, objects with __del__() methods, as well as generators with finally clauses, can be finalized when they are part of a reference cycle.
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This has been a notorious limitation in Python forever, and in 3.4 it's finally solved.
I am not into the Python internals but I would suspect the widely critiqued Python 3 step was just that: a shift that did not bring that much by itself but rearranged the inners enough to allow unlocking a lot of new doors in the future.
" This PEP removes the current limitations and quirks of object finalization. With it, objects with __del__() methods, as well as generators with finally clauses, can be finalized when they are part of a reference cycle. "
This has been a notorious limitation in Python forever, and in 3.4 it's finally solved.