what is the difference between append and insert in python lists

Question

when working in a list. if i want to add a value, what is the difference between append and insert?

can you show me an example as well?

Comments

Append adds to the end of the list, while insert adds in front of a specified index. Insert is slower when compared to append.

Answer 1

There is a simple difference between append and insert in python list,
append method can be use for adding new element in the list only but by using insert we can add as well as can modify already occupied position.
append method takes one argument (which you have to insert in the list) while insert method takes two elements (first will be the position of element and second will the element itself), Below are examples for both methods use:

Use of Append:

list = [1,2,3,4,5]

list.append(6)

print(list) # [1,2,3,4,5,6]

Use of Insert:

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

list.insert(5, 10) # [1,2,3,4,5,10]

list.insert(1, 10) # [1,10,3,4,5]
 

You can insert element at any position, but till will be store just after the last element position. Reason behind this logic is list is store data in ordered format. 

list.insert(100, 50) # [1,2,3,4,5,10]

Hope this helps!!

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Thanks!

Comments

Thanks, @Harshdeep, that was a very clear explanation.

Answer 2

Append method:- Append method adds a new element at the end of the list. The length of the list increases by one

Example:- new_list = [ 'a','b']

                 new_list.append( 'c' )

                 print(new_list)

Output:- [ 'a','b','c' ]

You can also append another list in the list.

another_list = [7, 2, 4, 3]

new_list.append(another_list)

print(new_list)

Insert method:- Insert method is the method which inserts a given element at a given index in a list. 

Syntax:- 

list_name.insert(index, element)

Example:-

new_list= [1,2,3,6,5,4 ]

new_list.insert(4,10)

print(new_list)

Output:- [1,2,3,6,10,5,4]

Answer 3

If we want to add an element in the List then we can use the append  method. using this element is add at last position of list but insert(a, x) function inserts an element at the position mentioned in its arguments. It takes 2 arguments, position and element to be added at respective positions.

#Program:
>>> a=[1,2,3,4,5]
>>> a.insert(1,4)#insert value 4 at 1 position
>>> a
[1, 4, 2, 3, 4, 5]
>>> a.insert(10,9)#if previous position not present then insert
#function add element at last position
>>> a
[1, 4, 2, 3, 4, 5, 9]

#Program:
>>> breakfast=["coffee","tea","toast","egg"]
>>> breakfast.append("salad")
>>> print(breakfast)
['coffee', 'tea', 'toast', 'egg', 'salad']

Answer 4

The difference is that with append, you just add a new entry at the end of the list. With insert(position, new_entry) you can create a new entry exactly in the position you want.

The append method adds a new item to the end of a list. It is also possible to add a new item to the end of a list by using the concatenation operator. On the other hand, with concatenation, an entirely new list is created. ...

Answer 5

Append():

This function is used to modify an already existing list. Adds a new specific element at the end of the list.

Syntax: List_Name.append(item)

Insert():

This function also modifies an already existing list. The only difference between append() and insert() is that insert function allows us to add a specific element at a specified index of the list unlike append() where we can add the element only at end of the list.

Syntax: List_Name.insert(index, item)

Refer below example for better understanding

Editor: Eclipse Luna with Pydev extension.