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

class LinkedList:
    def __init__(self): self.head = None
    def prepend(self, value): self.head = Node(value, self.head)
    def to_list(self):
        result, current = [], self.head
        while current is not None:
            result.append(current.value)
            current = current.next
        return result

linked = LinkedList()
for item in (3, 2, 1): linked.prepend(item)
assert linked.to_list() == [1, 2, 3]
print(linked.to_list())