Adding and Removing List Elements: Detailed Explanation of append() and pop() Methods

In Python, a list is a flexible data container that allows element addition and removal using the `append()` and `pop()` methods. `append()` is used to **add a single element to the end of the list** (directly modifying the original list). Its syntax is `list_name.append(element)`. If adding a mutable object (such as another list), only a reference to the object is stored; subsequent modifications to the original object will affect the result (e.g., changes to the sublist will be reflected). This method can only add one element at a time; multiple elements require repeated calls. `pop()` is used to **remove and return a specified element**. By default, it removes the last item (index `-1`). Its syntax is `list_name.pop(index)` (an out-of-bounds index will raise an `IndexError`). Indexes start at `0`, and negative numbers count backward from the end (e.g., `-1` refers to the last item). The core difference between the two is: `append()` only adds elements, while `pop()` requires specifying an index (defaulting to the last element). When using these methods, attention must be paid to the reference of mutable objects and the validity of the index—these are fundamental skills for list operations.