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This used to work perfectly with 2.92 but now fails with 3.0
preferences = bpy.context.preferences
cycles_preferences = preferences.addons["cycles"].preferences
cuda_devices, opencl_devices = cycles_preferences.get_devices()
with message TypeError: cannot unpack non-iterable NoneType object
Is there some change I can't find the docs to?
Because cycles_preferences.get_devices() is returning None. You want cycles_preferences.devices instead. But that may fail with a different error if you have more than two entries in devices. On my system, that's currently returning 3 devices.
If you try get_devices and a Tab for completion in the Python console you get this:
>>> cycles_preferences.get_devices(
get_devices(self, compute_device_type='')
# Deprecated: use refresh_devices instead.
But further investigation says that just updates the device list. So your code should probably be
preferences = bpy.context.preferences
cycles_preferences = preferences.addons["cycles"].preferences
cycles_preferences.refresh_devices()
cuda_devices = cycles_preferences.devices[0]
opencl_devices = cycles_preferences.devices[1]
