Clone linked list

clone_linked_list.py

class Node(object):

    def __init__(self, data):
        self.data = data
        self.next = None


def clone(cur):
    start = cur
    prev = None
    new_list_head = None
    while True:
        new = Node(cur.data)
        if not new_list_head:
            new_list_head = new
        if prev:
            prev.next = new
        cur = cur.next
        prev = new
        if cur == start:
            break
        prev = new
    return new_list_head


n1 = Node(10)
n2 = Node(20)
n3 = Node(30)
n4 = Node(40)

n1.next = n2
n2.next = n4
n3.next = n1
n4.next = n3

s = n = clone(n1)
while True:
    print(n.data)
    n = n.next
    if s == n:
        break