Is it possible to use the built-in len() function to determine the length of a singly linked list in Python?

The built-in len() function in Python does not work for singly linked lists if they are implemented manually (for example, through nodes with a pointer to the next element). len() works with sequences and collections that implement the __len__() method.

If you have a singly linked list class, to get its length, you need to either:

• Store a counter of elements inside the class and update it when adding/removing elements
• Or traverse all nodes and count manually

Example of counting the length of a singly linked list:

class Node:
    def __init__(self, value):
        self.value = value
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

    def length(self):
        count = 0
        current = self.head
        while current:
            count += 1
            current = current.next
        return count

Therefore, len() cannot be used directly unless you implement the __len__ method in the list class.