Python List append() Method

The Python List append() method is used to add new objects to a list. This method accepts an object as an argument and inserts it at the end of the existing list. The object argument can be of any type, as a Python list can hold multiple data type elements. However, if the object is itself a new list with multiple elements, it is considered as a single object and the size of the existing list will only be increased by 1.

Since we can append only a single object to the list at a time using this method, the time complexity of the append() method will be O(1).

Syntax

Following is the syntax for the Python List append() method −

list.append(obj)

Parameters

• obj − This is the object to be appended in the list.

Return Value

This method does not return any value but updates existing list.

Example

The following example shows the usage of Python List append() method. Here, we are creating a simple list containing string elements and trying to append another string element to it using this method.

aList = ['123', 'xyz', 'zara', 'abc'];
aList.append('2009');
print("Updated List : ", aList)

When we run above program, it produces following result −

Updated List :  ['123', 'xyz', 'zara', 'abc', '2009']

Example

Now, let us consider an example scenario where we append the missing days of a week into a Python list. In this example, a list is created containing the days of the week ['Mon', 'Tue', 'Wed']. Using the append() method, we will try to append the remaining days of the week in two ways: appending one element at a time and appending a list.

list = ['Mon', 'Tue', 'Wed']
print("Existing list\n",list)
# Append an element
list.append('Thu')
print("Appended one element: ",list)

# Append a list
list.append(['Fri','Sat'])
print("Appended a list: ",list)

Running the above code gives us the following result −

Existing list
['Mon', 'Tue', 'Wed']
Appended one element: ['Mon', 'Tue', 'Wed', 'Thu']
Appended a list: ['Mon', 'Tue', 'Wed', 'Thu', ['Fri', 'Sat']]

Example

The append() method can also be called on a list containing other data types rather than just strings. In the following example, we are trying to append an integer object to an integer list using this method.

# Creating an integer list
nums = [1, 2, 3, 4]
# Displaying the list
print('List Before Appending:')
print(nums)
print()
# Appending an element to the nums
# 5 will be added at the end of the nums
nums.append(5)
# Displaying the list
print('List After Appending:')
print(nums)

If you run the above program, you will get the following result −

List Before Appending:
[1, 2, 3, 4]
List After Appending:
[1, 2, 3, 4, 5]