How to assign to repeated field?
As per the documentation, you aren't able to directly assign to a repeated field. In this case, you can call extend to add all of the elements in the list to the field.
person.id.extend([1, 32, 43432])
If you don't want to extend but overwrite it completely, you can do:
person.id[:] = [1, 32, 43432]
This approach will also work to clear the field entirely:
del person.id[:]