[throwaway894345]

It took more than a decade for the ecosystem to migrate. IIRC, a lot of effort went into making them compatible, but some things are just fundamentally incompatible and also very difficult to automate (e.g., string encodings).

[mkl95]

I learnt Python in 2013, when Python 3 still had some serious growing pains. I switched from 2 to 3 almost overnight circa 2015 or 2016.

The last few years I cannot help but feel they were very close to making 2 and 3 play nice together, but the idea ironically lost traction because of how much Python 3 adoption had accelerated.

[throwaway894345]

Python 3 is easy for a Python 2 programmer to pick up, but that doesn’t mean it’s easy to port large systems from one to the other.