What is the difference between Python's list methods append and extend?

 

In Python, append and extend are two different methods used to add elements to a list, but they behave differently:

1. append:
   • The append method is used to add a single element to the end of a list.
   • It takes one argument, which is the element you want to add to the list.
   • The element is added as a single item, whether it's a value, a variable, or even another list. It becomes a new element within the original list.

Example using append:

python

my_list = [1, 2, 3]
my_list.append(4)
print(my_list)  # Output: [1, 2, 3, 4]

my_list.append([5, 6])
print(my_list)  # Output: [1, 2, 3, 4, [5, 6]]

In this example, append(4) adds the integer 4 as a single element to the end of the list, and append([5, 6]) adds the list [5, 6] as a single element to the end of the list.

2. extend:
   • The extend method is used to add multiple elements to the end of a list.
   • It takes an iterable (e.g., a list, tuple, or string) as an argument, and it adds each element from the iterable to the end of the list.
   • The elements from the iterable are added individually, not as a single unit. They become part of the original list, not nested within it.

Example using extend:

python

my_list = [1, 2, 3]
my_list.extend([4, 5])
print(my_list)  # Output: [1, 2, 3, 4, 5]

my_list.extend("abc")
print(my_list)  # Output: [1, 2, 3, 4, 5, 'a', 'b', 'c']

In this example, extend([4, 5]) adds the elements 4 and 5 individually to the end of the list, and extend("abc") adds the characters 'a', 'b', and 'c' individually to the end of the list.

To summarize:

• append adds a single element (which can be a value or another list) as a single unit to the end of the list.

• extend adds multiple elements from an iterable (such as a list or string) individually to the end of the list.

The choice between append and extend depends on your specific use case and whether you want to add a single item or multiple items to a list.