Today we’ll learn how to extend lists with elements from other lists, tuples and strings.
Here’s the video version of this article:
If you use the append method to append a list to another list, the whole list is added as an element of the other list, like in this example:
>>> main_list = [2, "ooops", 1]
>>> list_of_numbers = [1, 4]
>>> main_list.append(list_of_numbers)
>>> main_list
[2, 'ooops', 1, [1, 4]]
But what if you want to add all the elements of the other list separately to the other list? Well, this is what extending a list means.
We use the extend method to add all the elements of a list, tuple or string (the characters) to a list:
>>> main_list = [2, "ooops", 1]
>>> list_of_numbers = [1, 4]
>>> main_list.extend(list_of_numbers) # adds elements of the list
>>> main_list
[2, 'ooops', 1, 1, 4]
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You can also add all the elements of a string to a list, so all the characters one by one:
>>> just_a_string = "wow"
>>> main_list.extend(just_a_string) # adds elements of the string
>>> main_list
[2, 'ooops', 1, 1, 4, 'w', 'o', 'w']
or all the elements of a tuple:
>>> tuple_of_acronyms = ("CNN", "FBI")
>>> main_list.extend(tuple_of_acronyms) # adds elements of the tuple
>>> main_list
[2, 'ooops', 1, 1, 4, 'w', 'o', 'w', 'CNN', 'FBI']
An alternative way to extend a list is by means of the += operator:
>>> main_list += [1, 2, 3]
>>> main_list
[2, 'ooops', 1, 1, 4, 'w', 'o', 'w', 'CNN', 'FBI', 1, 2, 3]
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