Deep Copy and Shallow Copy in Python (original) (raw)

Last Updated : 5 Feb, 2026

In Python, assignment statements create references to the same object rather than copying it. Python provides the copy module to create actual copies which offer functions for **shallow (copy.copy()) and **deep (copy. deepcopy ()) copies. In this article, we will explore the main difference between Deep Copy and Shallow Copy.

Deep copy in Python

• A deep copy creates a new compound object before inserting copies of the items found in the original into it in a recursive manner.
• It will first construct a new collection object and then recursively populate it with copies of the child objects found in the original. It means that any changes made to a copy of the object do not reflect in the original object.

Syntax of Python Deepcopy

copy.deepcopy()

Example:

Python `

import copy

a = [[1, 2, 3], [4, 5, 6]]

Creating a deep copy of the nested list 'a'

b = copy.deepcopy(a)

Modifying an element in the deep-copied list

b[0][0] = 99 print("b: ", b) print("a: ", a)

`

Output

b: [[99, 2, 3], [4, 5, 6]] a: [[1, 2, 3], [4, 5, 6]]

**Explanation:

• **copy.deepcopy() method creates a completely independent copy of the original object, including all nested elements. Changes made to **deep_copied do not affect the original list a.
• nested elements of the original list a are recursively duplicated to ensure that even deeply nested objects are entirely independent in the copied list.

Shallow copy in Python

• A shallow copy creates a new object but retains references to the objects contained within the original. It only copies the top-level structure without duplicating nested elements.
• Changes made to a copy of an object do reflect in the original object. In python, this is implemented using the "copy.copy()" function.

Syntax of Python Shallowcopy

copy.copy()

Example:

Python `

import copy

a = [[1, 2, 3], [4, 5, 6]]

Creating a shallow copy of the nested list 'original'

b = copy.copy(a)

Modifying an element in the shallow-copied list

b[0][0] = 99

Printing the original and shallow-copied lists

print("b: ", b) print("a: ", a)

`

Output

b: [[99, 2, 3], [4, 5, 6]] a: [[99, 2, 3], [4, 5, 6]]

**Explanation:

• A shallow copy only copies the outer structure, retaining references to the nested objects. In this case, the inner lists are shared between original and **shallow_copied.
• As a result, changes to the nested elements in shallow_copied (e.g., modifying shallow_copied[0][0]) are also reflected in original.