Q.Fill in the blank : ___________ is not a valid built-in function for list manipulations.

Concept: Built-in methods of Python list objects

Python lists have specific methods attached to them for manipulation. We need to identify which option is not a valid list method.

Step 1: Check count() — this is a valid list method that returns the number of occurrences of a value: [1, 2, 2].count(2) gives 2.

Step 2: Check length() — Python does not have a length() method for lists. To find the length, we use the built-in function len(list), not list.length(). …

Python lists come with a suite of built-in methods that let you manipulate them directly. The key is knowing which operations are methods (called on the list itself, like my_list.append(x)) versus which are standalone functions (like len(my_list)).

Let's examine each option:

1. count() — This is a valid list method. It returns the number of times a specified element appears in the list. For example, [1, 2, 2, 3].count(2) returns 2.

2. length() — This does not exist as a list method in Python. Many students coming from other languages (like JavaScript's array.length property) expect this, but Python uses the built-in function len(my_list) instead. There is no my_list.length() method.

3. append() — A fundamental list method that adds a single element to the end of the list. my_list.append(5) modifies the list in place. …