How to Append List to Another List in Python? – list.extend(list)

Python – Append List to Another List – extend()

To append a list to another list, use extend() function on the list you want to extend and pass the other list as argument to extend() function.

In this tutorial, we shall learn the syntax of extend() function and how to use this function to append a list to other list.

Syntax – extend()

Following is the syntax of extend() function.

list1.extend(list2)

where elements of list2 are appended to the elements of list1.

extend() does inplace update to the original list list1. The function returns None.

Example 1: Append a list to another list

In the following example, we will create two lists and append the second list to the first one.

Python Program

#initialize lists
list1 = [6, 52, 74, 62]
list2 = [85, 17, 81, 92]
#extend first list with the second one
list1.extend(list2)
#print the extended list
print(list1)

Run

Output

[6, 52, 74, 62, 85, 17, 81, 92]

The contents of the list1 are modified.

Example 2: Append a list to another list keeping a copy of original list

If you would like to keep the contents of original list unchanged, copy the list to a variable and then add the other list to it.

Python Program

#initialize lists
list1 = [6, 52, 74, 62]
list2 = [85, 17, 81, 92]
#make of copy of list1
result = list1.copy()
#append the second list
result.extend(list2)
#print resulting list
print(result)

Run

Output

[6, 52, 74, 62, 85, 17, 81, 92]

list1 is preserved while the resulting extended list is in result.

Example 3: Append a list to another list – For Loop

You can also use a For Loop to iterate over the elements of second list, and append each of these elements to the first list using list.append() function.

Python Program

#initialize lists
list1 = [6, 52, 74, 62]
list2 = [85, 17, 81, 92]
#append each item of list2 to list1
for item in list2:
    list1.append(item)
#print the extended list
print(list1)

Run

Output

[6, 52, 74, 62, 85, 17, 81, 92]

Summary

In this tutorial of Python Examples, we learned how to extend a list with another list appended to it, with the help of well detailed example programs.