Hi this might be a long shot but if you're using windows or linux you should be able to retrieve information from either the system logs (linux, command: dmsg) or the device manager (windows, something to do with DEVCON in command line ) both would say an arduino UNO would be inserted (I'm using an Arduino UNO on windows at the mo and it's listed as Arduino UNO R3 (COM 5) where com 5 is the current port it's connected to)
You could have something in the python script along the lines of
On startup
search either dmesg (grep arduino) or windows devcon for currently connected arduno boards (you can import OS in python call any command line command and any results are returned as strings)
go through the result until you find the com port needed (or device path on linux e.g /dev/ttyACM0)
set that as the arduino's port in the python script
Hope this can be of help.