Python list insert Function | at End, Front, List into List Examples

Python list insert function is used to insert (add) elements in List. insert() is an inbuilt function in Python.

With the insert() method you can inserts the specified value at the specified position.

Syntax

list.insert(index, element)

Parameters

  • index – where an element needs to be inserted. (Required)
  • element – this is the element to be inserted in the list. (Required)

Return value

It doesn’t return anything.

Example of Python list insert() Function

1. Inserting Element to List

In the below example we are adding a number 7 at position 0;

# List
list1 = [1, 2, 3, 4, 5, 6]

# Inserting value
list1.insert(0, 7)

print("New List: ", list1)

Output:

New List: [7, 1, 2, 3, 4, 5, 6]

2. insert at “End”

Let’s see how to insert an element at the end of the Python list.

In the insert method use len() function at index value.

insert(len(a),7)

Example code:

# List
list1 = [1, 2, 3, 4, 5, 6]

# Inserting value
list1.insert(len(list1), 7)

print("New List: ", list1)

Output:

New List: [1, 2, 3, 4, 5, 6, 7]

Note: If given index >= length(list) is given, then it inserts at the end of the list.

3. insert at “Front”

You can insert an element in the python list insert at the front using the below code:-

Just use index value 0 –

list1.insert(0,element)
# List
list1 = ["a", "b", "c", "d"]

# Inserting value
list1.insert(0, "First")

print("New List: ", list1)

Output:

New List: [‘First’, ‘a’, ‘b’, ‘c’, ‘d’]

What is the Python list insert complexity?

According to Python’s official Time Complexity page1, using list.insert always has O(n) (linear) complexity.

TypeError: insert() function

According to the documentation, the insert method takes 2 positional (ordering matters) arguments. If you miss anyone will get an error.

# List
list1 = ["a", "b", "c"]

# Inserting value
list1.insert("d")

print("New List: ", list1)

Output:

TypeError: insert() takes exactly 2 arguments (1 given)

Python list insert Function example

Q: How to remove elements from the list in Python?

Answer: Use python remove() function to remove or delete elements from a list.

Read this tutorial for complete examples and codes – Python list remove() function

Q: Is it possible to insert a List into List in Python?

Answer: Yes you can Insert the list into another list. An insert() method, can insert one element by 1 at a time.

You can’t do it like that:-

list1.insert(0, list2)
list1 = [4, 5, 6, 3, 9]
list2 = [2, 3]

# printing original list 
print("List 1 : " + str(list1))

for i in range(len(list2)):
    list1.insert(i, list2[i])

# printing result
print("The list 1 after insertion: " + str(list1))

Output:

List 1 : [4, 5, 6, 3, 9]
The list 1 after insertion: [2, 3, 4, 5, 6, 3, 9]

Q: Can you Insert a Tuple (as an Element) to the List

Answer: Yes, you can insert a tuple as an element into the list.

# List
list1 = ["a", "b", "c"]

# number tuple
number_tuple = (3, 4)

# Inserting value
list1.insert(0, number_tuple)

print("New List: ", list1)

Output:

New List: [(3, 4), ‘a’, ‘b’, ‘c’]

Do comment if you have any doubts and suggestions on this tutorial.

Note: This example (Project) is developed in PyCharm 2020.1 (Community Edition)
JRE: 1.8.0
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.15.4
Python 3.7
All Python Programs code is in Python 3, so it may change its different from python 2 or upgraded versions.


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