myQueue

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


class Queue:
    def __init__(self):
        self.head = None
        self.tail = None
        self.length = 0
    
    
    def peek(self):
        return self.head.value
    
    
    def enqueue(self, value):
        if self.isEmpty():
            newNode = Node(value)
            self.tail = newNode
            self.head = newNode
        else:
            newNode = Node(value)
            self.tail.next = newNode
            self.tail = newNode
        self.length+=1
    
    
    def dequeue(self):
        if self.isEmpty():
            raise Exception("Queue is empty.")
        elif self.head == self.tail:
            returnVal = self.head.value
            self.head = None
            self.tail = None
        else:
            returnVal = self.head.value
            self.head = self.head.next
        self.length-=1
        return returnVal
    
    def isEmpty(self):
        return (True if self.length == 0 else False)
    
    
print("Hello World!")
myQueue = Queue()

print(myQueue.isEmpty())
assert(myQueue.isEmpty() == True)

myQueue.enqueue("Jason")
myQueue.enqueue("Joseph")
assert(myQueue.isEmpty() == False)

myQueue.enqueue("Caroline")
assert(myQueue.peek()=="Jason")

print(myQueue.dequeue())
assert(myQueue.peek()=="Joseph")
print(myQueue.dequeue())
assert(myQueue.peek()=="Caroline")
print(myQueue.dequeue())
assert(myQueue.isEmpty() == True)

try:
    print(myQueue.dequeue())
except Exception as e:
    print(f"exception: {e}")

print("Goodbye Cruel World")