Python List append() Method

append() method in Python is used to add a single item to the end of list. This method modifies the original list and does not return a new list. Let’s look at an example to better understand this.

a = [2, 5, 6, 7]

# Use append() to add the element 8 to the end of the list
a.append(8)
print(a)

[2, 5, 6, 7, 8]

Explanation: append(8) adds 8 to the end of the list a, modifying it in place.

Syntax of append() method

list.append(element)

Parameter:

• element: The item to be appended to the list. This can be of any data type (integer, string, list, object, etc.). This parameter is mandatory, and omitting it will cause an error.

Return:

• append() does not return any value. It modifies the original list in place.

Examples of append() Method

Here are some examples and use-cases of list append() function in Python.

1. Appending Elements of Different Types

The append() method allows adding elements of different data types (integers, strings, lists or objects) to a list. Python lists are heterogeneous meaning they can hold a mix of data types.

a = [1, "hello", 3.14]

a.append(True)
print(a)

[1, 'hello', 3.14, True]

Explanation: In this list “a” contains elements of different data types (integer, string, float) and append(True) adds a boolean True to the end of the list.

2. Appending List to a List

When appending one list to another, the entire list is added as a single element, creating a nested list.

a = [1, 2, 3]

a.append([4, 5])
print(a)

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

Explanation: append() method adds the list [4, 5] as a single element to the end of the list a, resulting in a nested list.

3. Appending Using a Loop

Appending multiple elements using a loop:

a = []
for i in range(5):
    a.append(i)
print(a)

[0, 1, 2, 3, 4]

Append vs Extend vs Insert

Example demonstrating the difference between append and extend:

a = [1, 2, 3]
a.append([4, 5])  
print(a)  

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

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

Explanation:

• append([4,5]) adds [4,5] as a single element, creating a nested list ([1, 2, 3, [4, 5]]).
• extend([4,5]) adds each element separately, resulting in [1, 2, 3, 4, 5].

Frequently Asked Questions on append() Method

Can append() add multiple elements at once?

No, append() can only add one element at a time. To add multiple elements we use the extend() method or we can use the append() method in a loop.

What is the time complexity of the append() method?

The append() method has a time complexity of O(1) (constant time) because it adds an element to the end of the list without requiring any resizing or reordering.

Can the append() method add an element at a specific index in the list?

No, the append() method only adds elements to the end of the list. If we need to insert an element at a specific index we can use the insert() method.

Can the append() method add another list to an existing list without creating a nested list?

No, the append() method will always add the entire list as a single element resulting in a nested list. To merge the contents of another list without nesting we use the extend() method instead.

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Article Tags :

• Python
• Python list-programs
• Python-Built-in-functions
• python-list
• python-list-functions

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Practice Tags :

• python
• python-list