I have a project where I am reading in ASCII values from a microcontroller through a serial port (looks like this : AA FF BA 11 43 CF etc) The input is coming in quickly (38
First of all, 38 two-character sets per second, 1 stop bit, 8 data bits, and no parity, is only 760 baud, not fast at all.
But anyway, my suggestion, if you're worried about having overly large lists/don't want to use one huge list, is just to store store a list on disk once it reaches a certain size and start a new list, repeating until you've gotten all the data, then combining all the lists into one once you're done receiving the data.
Though you may skip the sublists completely and just go with nmichaels' suggestion, writing the data to a file as you get it and using a small circular buffer to hold the received data that has not yet been written.