[pjmlp]

In Smalltalk, p x * 2 has that flow that as well, and even worse, lets assume the value returned by p x message selector, does not understand the * message, thus it will break into the debugger, then the developer will add the * message to the object via the code browser, hit save, and exit the debugger with redo, thus ending the execution with success.

Somehow Smalltalk JIT compilers handle it without major issues.

[ActivePattern]

Smalltalk JITs make p x * 2 fast by speculating on types and inserting guards, not by skipping semantics. Python JITs do the same (e.g. PyPy), but Python’s dynamic features (like __getattribute__, unbounded ints, C-API hooks) make that harder and costlier to optimize away.

You get real speed in Python by narrowing the semantics (e.g. via NumPy, Numba, or Cython) not by hoping the compiler outsmarts the language.

[afiori]

Python'a JIT could do the same, it could check if __getattribute__() is the default implementation and replace its call with p x directly. This would work only for classes that have not been modified at runtime and that do not implement a custom __getattribute__

[pjmlp]

People keep forgetting about image based semantics development, debugger, meta-classes, messages like becomes:,...

There is to say everything dynamic that can be used as Python excuse, Smalltalk and Self, have it, and double up.

[tekknolagi]

If I may toot my own horn: https://bernsteinbear.com/blog/typed-python/

[cma]

edit and continue is available on lots of JIT-runtime languages