Serial ports - any libraries for them out there?

Hi all :)

I'm currently playing around with some stuff involving reading/writing to/from serial ports. I am not really having any trouble doing that on Posix, but I'm wondering if there are any platform independant libraries of any kind out there for this. Just Posix & Windows would be nice.

I'm actually writing the code that uses the serial ports in Python, but I can write C extension modules for Python pretty easily.

All I want to eventually do is send and receive string data line by line (ie if I send "AT\r" to a modem I should receive "OK\r" next time I read from that port).

Thanks for any tips :)