I still haven't spotted a working solution to the problem where weather station programs in Python on Raspberry Pi fail, with no traceback details, after a couple of days.
I think it must be some resource in either the operating system, or the Python interpreter, running out, with very poor error reporting. I will leave it to people more familiar with the OS and interpreter to find out what it is, and fix it, in the fairly certain knowledge that everyone who could fix it has better things to do.
I found out that a Python program can actually restart itself, and changed mine to restart once a day. If that doesn't fix it, I'll let you know...