class Node(object): 
    def __init__(self, data, next):
        self.data = data
        self.next = next
 
D = Node(4, None)
C = Node(3, D)
B = Node(2, C)
A = Node(1, B)
 
E = Node(5,None)
F = Node(6,None)
 
def insert(nodeX, nodeY):
    pass
 
 
def pre_insert(nodeX, nodeY):
    pass
 
 
def printlist():
    tmp = A
    print("data is")
    while tmp.next is not None:
        print(tmp.data)
        tmp = tmp.next
    print(tmp.data)
 
printlist() # 1 , 2, 3, 4
 
insert(C, E)
printlist() # 1, 2, 3, 5, 4
 
pre_insert(C, F)
printlist() # 1, 2, 6, 3, 5, 4

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