A local *unexecuted* import appears to be changing the namespace. Attached files are ready to run. # over.py SOMETHING = "overridden" # main.py OVERRIDE = False SOMETHING = "original" def main(): #global SOMETHING # uncomment and it works if OVERRIDE: from over import SOMETHING # comment out and it works pass print SOMETHING # UnboundLocalError: local variable 'SOMETHING' referenced before assignment The SOMETHING variable has a value from the module global namespace, but it gets lost due to an import that is never executed. I would think an unexecuted statement shouldn't have any effect on anything. The second file will have to be submitted in a follow-on, it appears
hippmr: the problem is that by importing SOMETHING inside that function you're creating a *local variable* called SOMETHING. If the override isn't executed, and SOMETHING isn't global, then that local variable doesn't exist - which is why you get that error. So even if the import isn't executed, its existence in the function tells Python that name is local to the function.
