Understanding the Python copy() Method: A Comprehensive Guide

In this tutorial, we will delve into one of Python’s built-in methods known as copy(). This method is used to create a copy of a list or dictionary. It’s an essential tool for any Python programmer, especially when dealing with mutable objects.

What is the copy() Method?

The copy() method in Python creates a new object which is a copy of an existing object. The original and copied objects are independent. Changes made to one do not affect the other.

Syntax of the copy() Method

# For lists
new_list = old_list.copy()

# For dictionaries
new_dict = old_dict.copy()

How to Use the copy() Method?

We’ll illustrate its usage through examples:

List Copy Example:

old_list = [1, 2, 3]
new_list = old_list.copy()
print(new_list)

This will output: [1, 2, 3]

Dictionary Copy Example:

old_dict = {'a': 1, 'b': 2}
new_dict = old_dict.copy()
print(new_dict)

This will output: {'a': 1, 'b': 2}

Difference Between Shallow and Deep Copying

The copy() method performs what is known as shallow copying. In shallow copying, if you modify the nested elements in your original list or dictionary, the changes will reflect in the copied list or dictionary. This is because shallow copy creates references to original nested objects.

On the other hand, deep copying creates a new and separate copy of the entire object or list with all elements also being copies. Therefore, changes to the original do not affect copied object and vice versa.

Conclusion

The copy() method is a handy tool when you want to duplicate lists or dictionaries without affecting the original data. However, remember that it performs a shallow copy, so modifications to nested elements in your original data structure can still impact your copied data structure.