mystuff[4] = 'apple' doesn't add an 'apple', it overwrites an existing element in a list of at least 5 elements, and del mystuff[4] actually does change the len

mystuff[4] = 'apple' doesn't add an 'apple', it overwrites an existing element in a list of at least 5 elements, and del mystuff[4] actually does change the length of the list. They aren't symmetric at all.