A mutable object can be modified after it is created. An immutable object cannot be changed after creation.

Mutable object

A list can be changed without creating a different list object:

numbers = [10, 20, 30]
numbers[0] = 100

print(numbers)
            

Output:

[100, 20, 30]
            

Immutable object

A string cannot be modified in place:

language = "Python"
language[0] = "J"
            

This produces a TypeError.

You can create a new string and assign it to the variable:

language = "Python"
language = "J" + language[1:]

print(language)
            

Output:

Jython