Copy: a new outer list can share its contents

Useful to know

copy.copy() makes a shallow copy, while copy.deepcopy() handles nested objects using deep-copy rules. Assigning another name does not create a copy at all. [1]

With a list of settings, modifying an inner dictionary can be visible through two shallow copies. Choose the behaviour according to the intended sharing. Deep copying cannot replace a clear decision about which data should remain shared.