Concate two lists in python using extend
Question:
I have two lists given below
l1=[1,2,3,4]
l2=[5,6,7,8]
If i perform l1.extend(l2) and print(l1), output is [1,2,3,4,5,6,7,8] as expected but if i assign it to a variable like b=l1.extend(l2) and print(b) the output is None.
Can anyone explain this why it is so ?
Answers:
extend() works in place and returns None so you get the output of l1.extend(l2) returned as None.
The reason is that l1.extend updates the object itself (l1) and doesn’t return anything.
From Python docs:
list.extend(iterable)
Extend the list by appending all the items from the iterable. Equivalent to a[len(a):] = iterable.
I have two lists given below
l1=[1,2,3,4]
l2=[5,6,7,8]
If i perform l1.extend(l2) and print(l1), output is [1,2,3,4,5,6,7,8] as expected but if i assign it to a variable like b=l1.extend(l2) and print(b) the output is None.
Can anyone explain this why it is so ?
extend() works in place and returns None so you get the output of l1.extend(l2) returned as None.
The reason is that l1.extend updates the object itself (l1) and doesn’t return anything.
From Python docs:
list.extend(iterable)
Extend the list by appending all the items from the iterable. Equivalent to a[len(a):] = iterable.