[cletus]

IPv6 is a perfect example of the second-system effect [1] as in it added a bunch of things no one needed (but might need someday) and didn't solve roaming. All IPv4 really needed was a bigger address space.

But as soon as you cross the mental threshold of making a breaking change (which expanding the IPv4 address space obviously was) then it's easier to convince yourself to make a bunch more breaking changes. And this is where Python3 really lost its way (IMHO).

One of the silliest design decisions in Python3 was (initially) removing the string prefixes like s and u. Now obviously Python2 defaulted to ASCII and Python3 defaulted to Unicode but this decision just made making libraries compatible with both, so much so that they added it back (around 3.2-3.3 IIRC).

There are also always decisions you make that in hindsight you wish you'd done differently (eg the mutable Date class in Java) but just because you're making breaking changes doesn't mean you should "fix" all of those. You still have to look at each one and ask yourself "does this really matter enough to justify changing it now?". The default answer is "no" and the bar for "yes" should be really high.

I feel like Python3 failed here too.

And look where we are. Python3 out in 2008 and we're still writing migration guides in 2019.

[1]: https://en.wikipedia.org/wiki/Second-system_effect

[mixmastamyk]

It's important to realize however that not everyone feels that way about Python3. I'm glad they fixed it and I wish they'd fixed more.