Being a little pedantic: PyPy is written[1] in RPython[2], which is a strict subset of Python, and is quite restricted in many ways (E.g. when I was experimenti

Being a little pedantic: PyPy is written[1] in RPython[2], which is a strict subset of Python, and is quite restricted in many ways (E.g. when I was experimenting with it a while ago, all file operations, including reading/writing, were done with file descriptors (NB. it was a while ago, so this might've changed)). So it's not as quite as easy to fiddle with as you might expect, but still significantly easier than CPython, I guess. [1]: http://doc.pypy.org/en/latest/architecture.html#pypy-the-python-interpreter http://doc.pypy.org/en/latest/architecture.html#pypy-the-pyt... [2]: http://doc.pypy.org/en/latest/faq.html#what-is-this-rpython-language http://doc.pypy.org/en/latest/faq.html#what-is-this-rpython-...