Python: Join List

There are several ways in python in which we can join tow or more list together. Comprehension of the list is an effective means of describing and constructing lists based on current lists of elements which needs to be processed in a similar manner.

1. Using + operator  

The use of “+” operator can easily add the whole of one list behind the other list and hence perform the concatenation.

list_1 = [1,2,3,4,5]
list_2 = [6,7,8,9]
list3 = list_1 + list_2
print(list3) 

Output: [1, 2, 3, 4, 5, 6, 7, 8, 9]

2. Using list comprehension

It is used for list concatenation. This method is one liner alternative to loop method.

list_1 = [1,2,3,4]
list_2 = [5,6,7,8]
Final_list = [y for x in [list_1, list_2] for y in x]
print(Final_list)

Output: [1, 2, 3, 4, 5, 6, 7, 8]

3. Using extend()

It is used to extend the given list in python.

list_1 = [1,2,3,4]
list_2 = [5,6,7,8]
list_1.extend(list_2)
print(list_1)

 Output: [1, 2, 3, 4, 5, 6, 7, 8]

4. Using * Operator:

This method is the new addition to list concatenation.

list_1 = [1,2,3,4]
list_2 = [5,6,7,8]
res_list = [*list_1, *list_2]
print(res_list)

Output: [1, 2, 3, 4, 5, 6, 7, 8]

5. Using append():

This method is also used to add item in list.

list_1 = [1,2,3,4]
list_2 = [5,6,7,8]

for x in list_2:
    list_1.append(x)

print(list_1)

Output: [1, 2, 3, 4, 5, 6, 7, 8]