Editing Python (programming language) (section)

===Unsupported implementations===
[[Stackless Python]] is a significant fork of CPython that implements [[microthread]]s. This implementation uses the [[call stack]] differently, thus allowing massively concurrent programs. PyPy also offers a stackless version.<ref name="AutoNT-73"/>

Just-in-time Python compilers have been developed, but are now unsupported:
* Google began a project named [[Unladen Swallow]] in 2009: this project aimed to speed up the Python interpreter five-fold by using [[LLVM]], and improve [[multithreading (computer architecture)|multithreading]] capability for scaling to thousands of cores,<ref name="AutoNT-74"/> while typical implementations are limited by the [[global interpreter lock]].
* [[Psyco]] is a discontinued [[just-in-time compilation|just-in-time]] [[run-time algorithm specialization|specializing]] compiler, which integrates with CPython and transforms bytecode to machine code at runtime. The emitted code is specialized for certain [[data type]]s and is faster than standard Python code. Psyco does not support Python&nbsp;2.7 or later.
* [[PyS60]] was a Python&nbsp;2 interpreter for [[Series 60]] mobile phones, which was released by [[Nokia]] in 2005. The interpreter implemented many modules from Python's standard library, as well as additional modules for integration with the [[Symbian]] operating system. The Nokia [[N900]] also supports Python through the [[GTK]] widget library, allowing programs to be written and run on the target device.<ref>{{cite web|title=Python on the Nokia N900|url=http://www.stochasticgeometry.ie/2010/04/29/python-on-the-nokia-n900/|website=Stochastic Geometry|date=29 April 2010|access-date=9 July 2015|archive-date=20 June 2019|archive-url=https://web.archive.org/web/20190620000053/http://www.stochasticgeometry.ie/2010/04/29/python-on-the-nokia-n900/|url-status=live}}</ref>