Python .extend()

In Python, the .extend() method adds the elements of an iterable (like a list, string, or tuple) to the end of the current list. Unlike .append(), which adds the entire object as a single element, .extend() adds each element individually.

This makes .extend() especially useful for combining lists or incorporating multiple values into an existing list.

Syntax

list.extend(iterable)

Parameters:

• iterable: An iterable (like a list, tuple, or string) whose elements are to be added to list.

Return value:

The .extend() method changes the list in place and returns None.

Example 1: Extending a List with Another List

This example uses .extend() to add the items from the grocery_new list to the end of the grocery list:

grocery = ['blueberries', 'eggs', 'artichoke']
grocery_new = ['milk', 'cookies']

grocery.extend(grocery_new)

print(grocery)

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Here is the output:

['blueberries', 'eggs', 'artichoke', 'milk', 'cookies']

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Example 2: Extending a List with a Tuple

This example uses .extend() to add the items from the targets tuple to the end of the to_do_list list:

to_do_list = ['respond to email', 'check github']
targets = (4, 1, 6, 20)

to_do_list.extend(targets)

print(to_do_list)

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Here is the output:

['respond to email', 'check github', 4, 1, 6, 20]

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Codebyte Example: Extending a List with a String

This example uses .extend() to add the characters of a string to the end of the letters list:

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Frequently Asked Questions

1. What is the difference between .append() and .extend()?

• .append() adds the entire object as a single element.
• .extend() adds elements one by one from the iterable.

2. Does .extend() return a new list?

No. .extend() modifies the list in place and returns None.

3. What happens if I pass a non-iterable object to .extend()?

If you pass a non-iterable object to .extend(), you’ll get a TypeError.