Exercise_3.py

class ListNode:
    """
    A node in a singly-linked list.
    """
    def __init__(self, data=None, next=None):
        self.data = data
        self.next = next
class SinglyLinkedList:
    def __init__(self):
        """
        Create a new singly-linked list.
        Takes O(1) time.
        """
        self.head = None

    def append(self, data):
        
        new_node = ListNode(data)

        if self.head is None:
            self.head = new_node
            return

        current = self.head
        while current.next:
            current = curren
    
        
    def find(self, key):
        
        current = self.head
        while current:
            if current.data == key:
                return current
            current = current.next
        return None
        
        
    def remove(self, key):

        current = self.head
        prev = None

        while current:
            if current.data == key:
                if prev:
                    prev.next = current.next
                else:
                    self.head = current.next
                return
            prev = current
            current = current.next