.append in python

In the context of lists, += concatenates 2 lists together, but .append adds an object to the end of a list. Here's an example:

>>> numbers = [1, 2, 3]
>>> numbers += 4
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate list (not "int") to list
>>> numbers += [4, 5, 6]
>>> print(numbers)
[1, 2, 3, 4, 5, 6]
>>> numbers.append(7)
>>> print(numbers)
[1, 2, 3, 4, 5, 6, 7]
>>> numbers.append([8, 9, 10])
>>> print(numbers)
[1, 2, 3, 4, 5, 6, 7, [8, 9, 10]]

In other words, when you use += with a list, it adds the contents of the 2nd list onto the end of the first so everything is in the same list. If you try to += a list with anything other than a list, it'll throw a TypeError because it needs to take a list. Using .append takes whatever you give it and puts it in the last index of the list. If you give it a number, it'll go on the end of the list without raising an error (as will any other data type). If you give it a list, that whole list will be placed inside the first list