In late December 2023, CPython core developer Brandt Bucher submitted a pull-request to add a JIT compiler to the Python 3.13 branch. This is a significant change for the CPython Interpreter and builds on the Specializing Adaptive Interpreter introduced in Python 3.11 by the same developer. A JIT compiler, or “Just in Time” compiler, compiles code into machine code when it is run for the first time. The current Python compiler already compiles code into bytecode, but a JIT compiler emits machine code. This JIT compiler proposed for Python 3.13 is a copy-and-patch JIT, which is a relatively new concept. It works by copying instructions for each command and filling in the bytecode arguments at runtime. Despite initial benchmarks showing a modest performance improvement of 2-9%, the real value of this JIT compiler lies in its potential for future optimizations and performance improvements.
https://tonybaloney.github.io/posts/python-gets-a-jit.html