What is the difference between Python’s list methods append and extend?

append appends a specified object at the end of the list:

>>> x = [1, 2, 3]
>>> x.append([4, 5])
>>> print(x)
[1, 2, 3, [4, 5]]

extend extends the list by appending elements from the specified iterable:

>>> x = [1, 2, 3]
>>> x.extend([4, 5])
>>> print(x)
[1, 2, 3, 4, 5]