python threads & sockets

Question

I have a "I just want to understand it" question.. first, I'm using python 2.6.5 on Ubuntu.

So.. threads in python (via thread module) are only "threads", and is just tells the GIL to run code blocks from each "thread" in a certain period of time and so and so.. and there aren't actually real threads here..

So the question is - if I have a blocking socket in one thread, and now I'm sending data and block the thread for like 5 seconds. I expected to block all the program because it is one C command (sock.send) that is blocking the thread. But I was surprised to see that the main thread continue to run. So the question is - how can GIL is able to continue and run the rest of the code after it reaches a blocking command like send? Isn't it have to use real thread in here?

Thanks.