In this week's Python snippet post we're looking at the extend method for lists.

extend is a lot like the append method, but instead of adding a single value, extend allows us to append several elements to the end of a given list object.

Let's start by defining a couple of lists:

l_1 = [1, 2, 3, 4]
l_2 = [5, 6, 7, 8]

We're going to use extend to add the values from l_2 onto the end of l_1:


print(l_1)  # [1, 2, 3, 4, 5, 6, 7, 8]

As we can see, the extend method in an in-place operation, so it modifies the original list. Other than that, it perform very similarly to using the + operator with lists, so why should we care about extend?

Well, extend can accept any iterable, while using something like + to perform concatenation only works when both objects are lists. So we can do this:

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

While the following will give us a TypeError:

[1, 2, 3] + (4, 5, 6)

Using extend on the other hand, everything works just fine:

l_1 = [1, 2, 3, 4]
t_1 = (5, 6, 7, 8)

l_1.extend(t_1)  # [1, 2, 3, 4, 5, 6, 7, 8]

Wrapping up

That's it for extend! I hope you learnt something new, and I hope you can find places to use extend in your own code.

If you're just starting out with Python, or you're just trying to improve, check out our Complete Python Course! We take you from beginner level right up to some pretty advanced Python, so it's a great place to develop your Python skills.

You might also want to check out our mailing list below, as we post regular discount codes for our subscribers, so that they can get the best deals on all our courses.