Python Copy List: Complete Guide with Examples

Copying lists in Python is useful when you need to work with duplicates without affecting the original list.

This guide covers several methods to copy a list with examples and explanations.

Using Slicing to Copy a List

One of the simplest ways to copy a list is with slicing. This creates a new list with the same elements.

fruits = ["apple", "banana", "cherry"]
new_fruits = fruits[:]
print(new_fruits)

['apple', 'banana', 'cherry']

Slicing fruits[:] returns a new list new_fruits that is independent of the original.

Using the list() Function

The list() function is another easy way to create a copy of a list.

It’s useful when you want a new list object, not a reference to the original list.

fruits = ["apple", "banana", "cherry"]
new_fruits = list(fruits)
print(new_fruits)

['apple', 'banana', 'cherry']

Using list(fruits) creates a new list new_fruits with the same contents.

Using the copy() Method

The copy() method is available in Python lists to create shallow copies.

This is effective when you don’t need a deep copy of nested lists.

fruits = ["apple", "banana", "cherry"]
new_fruits = fruits.copy()
print(new_fruits)

['apple', 'banana', 'cherry']

With copy(), new_fruits is an independent list from fruits.

Using the copy Module for Deep Copies

If you’re copying a list of lists or other nested objects, you’ll need a deep copy to avoid references to the original.

The copy.deepcopy() function from the copy module is perfect for this.

import copy

nested_list = [[1, 2, 3], [4, 5, 6]]
new_nested_list = copy.deepcopy(nested_list)
print(new_nested_list)

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

Using copy.deepcopy() creates a new copy of nested_list without linking to the original list.

Using List Comprehension

List comprehensions are useful for copying lists while applying transformations.

This method is best for creating modified copies.

fruits = ["apple", "banana", "cherry"]
new_fruits = [fruit for fruit in fruits]
print(new_fruits)

['apple', 'banana', 'cherry']

In this example, [fruit for fruit in fruits] returns a new list identical to fruits.

Conclusion

With options like slicing, list(), and copy(), Python makes it easy to copy lists.

Learn more about list manipulation in Adding a List to Another List in Python.

Using these methods, you can confidently manage lists in Python without accidental modifications.