append() and extend() in Python

The append() and extend() functions are used with the python list to increase its number of elements. But the two have different behaviors as shown below.

append()

Syntax: list_name.append(‘value’)
It takes only one argument.

This function appends the incoming element to the end of the list as a single new element. Even if the incoming element is itself a list, it will increase the count of the original list by only one.

Example

list = ['Mon', 'Tue', 'Wed' ]
print("Existing list\n",list)
# Append an element
list.append('Thu')
print("Appended one element: ",list)

# Append a list
list.append(['Fri','Sat'])
print("Appended a list: ",list)

Output

Running the above code gives us the following result −

Existing list
['Mon', 'Tue', 'Wed']
Appended one element: ['Mon', 'Tue', 'Wed', 'Thu']
Appended a list: ['Mon', 'Tue', 'Wed', 'Thu', ['Fri', 'Sat']]

extend()

Extend adds each element to the list as an individual element. The new length of the list is incremented by the number of elements added.

Syntax: list_name.extend(‘value’)
It takes only one argument.

Example

list = ['Mon', 'Tue', 'Wed' ]
print("Existing list\n",list)
# Extend an element
list.extend("Thu")
print("Extended one element: ",list)

# Extend a list
list.extend(['Fri','Sat'])
print("Extended a list: ",list)

Output

Running the above code gives us the following result −

['Mon', 'Tue', 'Wed']
Extended one element: ['Mon', 'Tue', 'Wed', 'T', 'h', 'u']
Extended a list: ['Mon', 'Tue', 'Wed', 'T', 'h', 'u', 'Fri', 'Sat']