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Python .append() and .extend() Methods

You can add elements to a list using the append method. The append() method adds a single element towards the end of a list.

Example of the append() method

For example, let’s extend the string by adding “April” to the list with the method append(). Using append() will increase the length of the list by 1.

list.append() adds a single element to a list

months = ['January', 'February', 'March']
months.append('April')
print(months)
['January', 'February', 'March', 'April']

Using list methods to add data: append() vs. extend()

The .append() method increases the length of the list by one, so if you want to add only one element to the list, you can use this method.

x = [1, 2, 3]
x.append(4)
x
[1, 2, 3, 4]

The .extend() method increases the length of the list by the number of elements that are provided to the method, so if you want to add multiple elements to the list, you can use this method.

x = [1, 2, 3]
x.extend([4, 5])
x
[1, 2, 3, 4, 5]

Interactive example of the append() and extend() methods

We start with the list names:

names =  ['Apple Inc', 'Coca-Cola', 'Walmart']
# Append a name to the list names
names.append('Amazon.com')
print(names)

When we run the above code, it produces the following result:

names =  ['Apple Inc', 'Coca-Cola', 'Walmart', 'Amazon.com']

We can then add two additional elements to the list names using extend() and the more_elements list.

# Extend list names
more_elements = ['DowDuPont', 'Alphabet Inc']
names.extend(more_elements)
print(names)

When we run the above code, it produces the following result:

['Apple Inc', 'Coca-Cola', 'Walmart', 'Amazon.com', 'DowDuPont', 'Alphabet Inc']

Try it for yourself.

To learn more about list methods and functions, please see this video from our course Introduction to Python for Finance.

This content is taken from DataCamp’s Introduction to Python for Finance course by Adina Howe.