
Description: Stackless Python is a Python programming language implementation featuring microthreads and no Global Interpreter Lock (GIL). It allows massive concurrency and offers better scalability for Python programs.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: PyPy is an alternative Python interpreter written in Python. It features a just-in-time compiler and supports many Python libraries and frameworks. PyPy focuses on speed, efficiency and compatibility with CPython.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API