Python extend() Function

The extend() function in Python, is used to add multiple elements or an iterable at the end of a list. For example:

a = [65, 7, 8]
print("The list a is:")
print(a)

a.extend([76, 890])
print("\nNow the list a is:")
print(a)

b = [1, 2, 78, 43]
a.extend(b)
print("\nNow the list a is:")
print(a)

The output produced by above Python program, demonstrating the extend() function is:

The list a is:
[65, 7, 8]

Now the list a is:
[65, 7, 8, 76, 890]

Now the list a is:
[65, 7, 8, 76, 890, 1, 2, 78, 43]

Note - It is not limited to add multiple elements using extend() every time. That is, you're free to add single element too at the end of a list, using this function.

Suggestion - If you want to add single element at the end of a list, go for append(), instead of extend(). Also, if you want to add an iterable such as list, tuples, set etc. itself at the end of a list in a way to make the list becomes nested list, then go for append().

Python extend() Function Syntax

The syntax to use extend() function is:

listName.extend([value1, value2, value3, ..., valueN])

Or

listName.extend(iterable)

iterable may be a list, tuple, set, etc.

Python extend() Function Example

Here is an example demonstrating the extend() function again, in Python:

a = ["codes", "cracker"]
b = {1, 2, 3}
a.extend(b)
print(a)

c = ['p', 'y', 't']
d = ('o', 'n')
c.extend(d)
print(c)

Here is its sample output:

['codes', 'cracker', 1, 2, 3]
['p', 'y', 't', 'o', 'n']

The program given below, also produces the same output as of above one:

a = ["codes", "cracker"]
a.extend({1, 2, 3})
print(a)

c = ['p', 'y', 't']
c.extend(('o', 'n'))
print(c)

Let's create another example program demonstrating the extend() function in Python:

a = ["codes", "cracker"]
b = (1, 2, 3)
c = {'c', 'o', 'm'}

a.extend(b)
a.extend(c)

print(a)

This program produces following output:

['codes', 'cracker', 1, 2, 3, 'c', 'o', 'm']

Here is another example demonstrates the extend() method in Python, with user input:

print("How many element to store in first list: ", end="")
tot = int(input())
print("Enter", tot, "elements for the first list: ", end="")
listOne = []
for i in range(tot):
    listOne.append(input())

print("How many element to store in second list: ", end="")
tot = int(input())
print("Enter", tot, "elements for the second list: ", end="")
listTwo = []
for i in range(tot):
    listTwo.append(input())

print("\nExtending the first list using second...")
listOne.extend(listTwo)
print("\nNow the list \"listOne\" is:")
print(listOne)

The snapshot given below shows the sample run of above Python program, with user input 3 as size of first list, codes, cracker, dot as its three elements, and 1 as size of second list, whereas com as its element:

python extend function

Note - The + operator can also be used to extend a list.

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