Implementing my own Python interpreter

[Robert Kern]

Ognjen Bezanov wrote:
> Hello All,
> 
> I am a third year computer science student and I'm the process of
> selection for my final year project.
> 
> One option that was thought up was the idea of implement my own version
> of the python interpreter (I'm referring to CPython here). Either as a
> process running on another OS or as a process running directly on the CPU.
> 
> Now, I can't seem to find a decent source of information on the python
> interpreter. I have made the assumption that Python works very much like
> Java, you have code that is compiled into bytecode, which is then
> executed in a virtual machine. IS this correct?

Mostly. It is worth noting, though, that the Python bytecode is at a higher 
level than Java bytecode. You can run other languages on top of the JVM using 
Java bytecode (Python, for one), but Python bytecode is geared very much towards 
running Python code with Python's object model.

> Is there a good source
> to give me an overview of Python internals? (I can look at the code, but
> I would find it easier to understand if I can see the "big picture" as 
> well)

Several years ago, there was someone who wrote up such a document for a 
university project. Unfortunately, my Google-fu has failed me, and I cannot find 
it again.

> Also, any pro's out there willing to chime on the feasibility of
> implementing python to run directly on the hardware (without an
> underlying OS)? I don't expect 100% compatibility, but would the basics
> (branching, looping, arithmatic) be feasible?

Sure. There have been a few ports to microcontrollers. For example, the 
GM862-QUAD-PY cellular module has an embedded Python 1.5.2 (plus a few 2.x 
features):

   http://www.gm862.com/en/products/gsm-gprs.php?p_id=12&p_ac=show&p=4

PyMite is an open source implementation for 8-bit microcontrollers:

   http://pymite.python-hosting.com/

TinyPy is similar, although I don't believe it ever aimed for (or has achieved) 
running OS-less:

   http://www.tinypy.org/

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco