What is the difference between shallow copy and deep copy?

A shallow copy creates a new object that is a copy of the original object, but it only duplicates the references to the objects contained in the original. This means that the new object and the original object share the same references; if any referenced objects are modified, those changes will be reflected in both the original and the shallow copy. Therefore, a shallow copy does not create duplicates of the referenced objects themselves.

In contrast, a deep copy creates a new object and recursively duplicates all objects referenced by the original object, resulting in a completely independent copy. This independence ensures that changes made to the deep copy do not affect the original object or its references.

Understanding this difference is crucial in programming, particularly in languages like Python, where managing mutable objects can lead to unintended consequences if shallow copies are used where deep copies are needed. The notion that "a shallow copy duplicates the object but not referenced objects" accurately encapsulates this concept.