- PyPy is an Interpreter that implements the Python programming language
- It is based on the RPython compiler framework for dynamic language implementations
- It is a replacement of CPython and it generally runs faster than that.
The main executable comes with a JIT Compiler. There are two cases defined in the documentation, where PyPy will not be able to speed up the Python code:
- Short-running processes: if it doesn’t run for at least a few seconds, then the JIT compiler won’t have enough time to warm up.
- If all the time is spent in run-time libraries (i.e. in C functions), and not actually running Python code, the JIT compiler will not help.
So, PyPy works best when executing long-running programs where majority of time is spent executing Python code.