LinkedList.py

class Node:
	def __init__(self, value=None, next=None):
		self.value = value
		self.next = next
	
	#print override
	def __repr__(self):
		return str(self.value)

class LinkedList:
	def __init__(self, head=None):
		self.head = head

	#generator override, can be used in for loop
	def __iter__(self):
		currNode = self.head
		while currNode:
			yield currNode
			currNode = currNode.next

	def __repr__(self):
		#Converting generator(__iter__) into list will expose the content
		#__repr__ needs return type to be of string
		return str(list(self))

	def insertAtFront(self, value):
		self.head = Node(value, self.head)

	def insertAtBack(self, value):
		if self.head is None:
			self.insertAtFront(value)
			return
		#this calls __iter__
		for currNode in self:
			if currNode.next is None:
				break
		currNode.next = Node(value)
	
	def removeFirst(self):
		if self.head is not None:
			self.head = self.head.next

	def removeLast(self):
		if self.head is None:
			return
		elif self.head.next is None:
			self.head = None
			return
		for currNode in self:
			if currNode.next.next is None:
				break
		currNode.next = None

def main():
	list = LinkedList()

	list.insertAtBack(4)
	list.insertAtBack(5)
	#this calls __repr__
	print list #[4, 5]
	list.insertAtFront(3)
	list.insertAtFront(2)
	list.insertAtFront(1)
	print list #[1, 2, 3, 4, 5]
	list.insertAtBack(6)
	list.insertAtBack(7)
	print list #[1, 2, 3, 4, 5, 6, 7]
	list.removeFirst()
	print list #[2, 3, 4, 5, 6, 7]
	list.removeLast()
	list.removeLast()
	list.removeLast()
	list.removeLast()
	list.removeLast()
	list.removeLast()
	print list #[]
	list.insertAtFront(1000)
	print list #[1000]
			
if __name__ == "__main__":
	main()