time complexity of append in python code example

Example 1: python add all values of another list

a = [1, 2, 3]
b = [4, 5, 6]
a += b
# another way: a.extend(b)

Example 2: extend in list python

subjects=["Maths","Science","Arts","Commerce"]
subjects_2=["Artificial intelligence","Statistics"]
subjects.extend(subjects_2)
print(subjects)  ## used to add more elements from other list