The thing I think they did better though, is they didn't give people 10 years to fix their sh*t. You either moved on or you stayed with an unsupported version, and people did move on.
For Python 3 the major shifts were in 2015 and 2020. The first year was when PSF announced they won't add any new features to 2.7, and that's when libraries started adding Python 3 support. And 2020 was EOL for Python 2.7.
It doesn't matter how much time you give people to migrate, they will always do it at the very last minute.
Also, 1.8 marked the creation of complete compliance test suite (as Ruby 1.8 became an ISO Standard), and that test suite has been expanded since then allowing for alternative implementations.
Because the test suite is your target, not a hard to interpret 2kLOC spaghetti code C function.
Ruby was then using a version numbering scheme similar to the old Linux version numbering scheme, where odd minor numbers were development releases and even minor numbers were stable releases. In that scheme a odd minor version is equivalent to a SemVer major release. (Ruby switched to SemVer-ish versions with 2.x)
It would be nice to have an alternative to Python that took backwards compatibility seriously. Might be easier to start from Python2 than to go from scratch. You might be able to add a REPL to perl5, but its syntax isn't the most beginner friendly I've ever seen.
Things these languages do have in common with Python3 are:
- support for keyword arguments and optional arguments
- support for objects and interfaces (but not necessarily for inheritance)
- handling of names in scopes and name spaces
- closures and lambdas
- list comprehensions
- arbitrarily long integers, complex numbers, a numeric tower
- an empty sequence or empty string is logically false (with a few nuances)
- low-level bit operations (often down to a very low level such as popcount in C)
- easy to call into C code (or Java code if it runs on the JVM)
- full unicode support
- conditional expressions like (a if boolval else b)
- type annotations
- string formatting forms a mini-language
- print is a function
- hexadecimal, octal, and binary literals
- tools for iteration and first-class functions, like partial application
- support for OOP
In addition to this, the members of the Lisp family usually have as well:
- strong support for functional programming
- full and efficient garbage collection
- persistent data structures
- compile to machine code (native code generation or JIT compilation)
- a powerful macro system
- capability to define custom control constructs
- support for pattern matching to members of compound objects, similar to
(a, b) = name[:2]
What exactly would be suited best depends IMO on the use case.
I think Racket is ideal for easy learning, a platform-independent GUI, and comprehensive documentation, and is also useful fir science applications. It can also interact well with C libraries (or, more generally native libraries with C interface), and it is good for scripting.
Clojure is ideal for server applications with a lot of concurrency and a high performance. Its concurrency support is brilliant and best-in-class, much better than Python.
Common Lisp / SBCL is somewhat under-hyped in comparison to Clojure, yet it has an excellent performance, integrates well with C libraries, has a highly interactive repl, a comprehensive library system (quicklisp), a standard build system (asdf), comprehensive documentation for beginners (common Lisp cookbook), it is very usable for scripting, has standard pthreads-like concurrency primitives, a powerful object system, and then some more.