Hmm, yes I see now that using settings.xml won’t work. Here’s another idea — try setting the OPENMC_CROSS_SECTIONS environment variable from the Python script:
import os
os.environ['OPENMC_CROSS_SECTIONS'] = 'Data000/cross_sections.xml'
The Operator class relies on that when it is instantiated, so if you want to run a bunch of depletion simulations from the same script, you’ll have to change os.environ and create a new instance of Operator each time.