How to copy a list in Python?
Table of Contents
Introduction
Copying a list in Python is an important operation when you need to work with the same data in multiple places without modifying the original list. Python provides several ways to copy a list, each serving different purposes depending on whether you want a shallow copy or a deep copy. In this guide, you'll learn how to copy lists using multiple techniques and when to use each one.
Methods to Copy a List in Python
1. Using the copy() Method (Python 3.3+)
The copy() method is the simplest and most straightforward way to create a shallow copy of a list. A shallow copy means that the copied list contains references to the objects in the original list rather than completely new objects.
Example:
2. Using List Slicing
List slicing is a common method to copy a list. By slicing with [:], you create a shallow copy of the list, similar to copy().
Example:
3. Using the list() Constructor
The list() constructor can also be used to create a shallow copy of a list. It constructs a new list object from the iterable passed to it.
Example:
4. Using copy.deepcopy() for Deep Copy
If the list contains nested lists or other mutable objects, and you want to copy everything (including nested objects), you need to use the copy.deepcopy() method. A deep copy duplicates the objects, ensuring that changes to the copied list do not affect the original one.
Example:
Practical Examples
Example : Shallow Copy of a Simple List
Example : Deep Copy of a Nested List
Conclusion
Copying a list in Python can be achieved using various methods like the copy() method, slicing, the list() constructor, and copy.deepcopy(). For simple lists, shallow copying with copy(), slicing, or list() is sufficient. However, for nested lists or lists containing mutable objects, deepcopy() is necessary to ensure full duplication. Understanding these techniques allows for better data handling and reduces unintended side effects in your code.