Python is, of course, a dynamic interpreted language rather than a static compiled language such as the one used by TouchDevelop. Furthermore, a version of Python that compiled to the TouchDevelop AST would be a completely new language - a Pythonic shim to make TouchDevelop feel like Python. Finally, TouchDevelop itself is written in TypeScript, an interesting Microsoft-developed language that compiles to JavaScript. None of us evaluating TouchDevelop knew TypeScript and the thought of creating a new compiler for a sort-of-Python, frankly, gave us the collywobbles.
Ultimately, designing and creating something Python-ish to work on TouchDevelop appeared to be impossibly difficult (or difficultly impossible, depending on how you looked at it) for a handful of volunteers working in their spare time in an unfamiliar language.
It was at this time that something amazing happened [ntoll.org].
I was at a partner's meeting at the BBC and, quite by accident, struck up a tea-break conversation with "Jonny from ARM, pleased to meet you". It turned out that Jonny is a fellow geek, but one that inhabits a different layer of the computing stack (I generally work in high level languages like Python or JavaScript, Jonny feels more at home close to the bare metal hacking hardware).
After we'd figured out the above, Jonny asked, "have you ever heard of MicroPython?" (MicroPython is a full re-implementation of Python 3 for microcontrollers used in small devices such as the micro:bit).