What is the difference between a shallow copy and a deep copy in Python?

A shallow copy creates a new container object but does not recursively copy nested objects; it only copies references to the nested objects. A deep copy recursively copies all objects found within the original, producing a completely independent clone. Use the copy module: copy.copy() for shallow, copy.deepcopy() for deep. Shallow copies are O(n) in the size of the container, while deep copies are also O(n) but with additional overhead for each nested object.