check linked list cycle | Python Fiddle

import random

class Node:
  def __init__(self):
    self.data = None # contains the data
    self.nextNode = None # contains the reference to the next node

# create a linked list without a cycle    
nonCycle = Node()
nonCycle.data = 1
current = nonCycle

for i in range(2,10):
  new_node = Node()
  new_node.data = i
  current.nextNode = new_node
  current = new_node

# create a list with a cycle    
cycle = Node()
cycle.data = 1
current = cycle
four = None

for i in range(2,8):
  new_node = Node()
  new_node.data = i
  current.nextNode = new_node
  current = new_node
  if i == 4: four = new_node
  if i == 7: new_node.nextNode = four

def detectCycle(head):
    
  toReturn = None
  foundCycle = False
  current = head
  while current.nextNode and not foundCycle:
    if not hashMap.get(current):  
      hashMap[current] = 1
      current = current.nextNode  
    else:
      print "Already in: " + str(current.data)        
      foundCycle = True
      toReturn = current
  return toReturn
    
    
print detectCycle(nonCycle)
print detectCycle(cycle)

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