Python request

Hi, I need something so I can start my mod.
Could anybody script for me something that would do the following:

At the beginning of a game, all techs are availables (I will redo techs)

When a player choose a tech, another one in the list RANDOMLY becomes unavailable. And so one......

The idea is to have "in the end" civilisations that will REALLY be different (just like aztecs(mathematic, calendar, religion) were different from vikings (seafaring, raiders, iron working) who were different from berbers (desert knowledge, religion, raiders...)

Please please please, i really need this piece of code, and some explanations on how to use it.

Hmm... I do believe it is very possible. The tricky part is how to tell the code which tech not to enable. If I have time, I'll see what I can whip up

Even just for answering.

If you can manage to do something, even the basics, and be so kind (and patient) as to tell me how to make it function, it would be, well, just great
I am a total non programmer, but I managed to learn bits of C++ to create NWN scripts. I tried really hard to understand and make python function, even learning from the many tutorials that exist on the web, but couldn't get into it. I tried so hard !!!! I will do all the other stuff, but just can't do this.
Please please please....

If you can find cannotResearch from one of civ's python files, it should help. Dunno if that exists though...

Another, easier but messier way, would be to create non-visible unabled techs in XML, and each default tech would require their specific one. Then you could very easily give & take away those unabled techs, effectively disabling some techs from being researched.

I rememeber from my previous studies of Python, that maybe that could be done from lists. But it's the code that I need, what you just said is nearly chinese to me :-(