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

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

In Python, a shallow copy creates a new object but inserts references into it to the objects found in the original. A deep copy, on the other hand, creates a new object and recursively adds copies of nested objects found in the original.

Can you give me an example of each?

Sure! For a shallow copy, you can use the copy module's copy() function. For a deep copy, use copy.deepcopy(). Here's a quick example:

import copy

original = [1, 2, [3, 4]]
shallow = copy.copy(original)
deep = copy.deepcopy(original)

shallow[2][0] = 'changed'
print(original)  # Output: [1, 2, ['changed', 4]]
print(shallow)   # Output: [1, 2, ['changed', 4]]
print(deep)      # Output: [1, 2, [3, 4]]

What happens if I modify the original object after making a shallow copy?

If you modify the original object, the changes will reflect in the shallow copy for any mutable objects. This is because the shallow copy contains references to the same nested objects.

How can I avoid this issue when using shallow copies?

To avoid this issue, you should use a deep copy instead, which creates entirely new instances of the nested objects, ensuring that changes to the original do not affect the copy.