PyPy

PyPy is an alternative implementation of the Python programming language designed to be fast and efficient while remaining compatible with Python code. It provides a Just-In-Time (JIT) compiler that translates hot Python paths into optimized machine code at runtime, often delivering substantial speedups for long-running processes.

PyPy is implemented using the RPython toolchain, a restricted subset of Python, and the project includes the interpreter, the JIT compiler, and a garbage collector. This combination aims to provide a self-contained runtime with improved performance characteristics over CPython in many scenarios.

Compatibility with CPython: PyPy aims to be compatible with the CPython API and the Python standard library. For extension modules written in C, PyPy offers a compatibility layer called cpyext, and many pure-Python libraries run without changes. However, some C extensions and platform-specific code may require additional work or are not supported.

Versions: PyPy provides PyPy3 for Python 3 compatibility; PyPy2 existed for Python 2 but has reached end of life. The project continually releases updates to improve performance, compatibility, and interoperability with the wider Python ecosystem.

Performance and usage: PyPy generally speeds up many workloads, especially long-running or CPU-bound tasks, but the JIT has warm-up overhead, so short scripts may not see benefits. It is used in various domains, including web services and data processing, where Python code runs for extended periods.

Availability: The PyPy project is actively maintained with releases and documentation available at pypy.org.