QueueArray.py

class Queue:
    def __init__(self):
        self.array = []

    def is_empty(self):
        return len(self.array) == 0

    def enqueue(self, value):
        self.array.append(value)
    
    def dequeue(self):
        if self.is_empty():
            return None
        val = self.array[0]
        self.array.remove(val)
        return val

QueueLinkedList.py

class LinkedList(object):
    def __init__(self, data = None):
        self.value = data
        self.next = None

class Queue:
    def __init__(self):
        self.first = None
        self.last = None

    def is_empty(self):
        return self.first == None

    def enqueue(self, value):
        node = LinkedList(value)
        if self.is_empty():
            self.first = node
            self.last = self.first 
        else:
            current_last = self.last
            current_last.next = node
            self.last = node
    
    def dequeue(self):
        if self.is_empty():
            self.last = None
            return self.last
        data = self.first.value
        next = self.first.next
        if next is None:
            self.first = None
            self.last = None
        else:
            self.first = next
        return data
      
q = Queue()
print q.dequeue()
q.enqueue('first')
print q.dequeue()
q.enqueue('1')
q.enqueue('2')
q.enqueue('3')
print q.dequeue()
q.enqueue('4')
print q.dequeue()
print q.dequeue()
print q.dequeue()
print q.dequeue()

# Output:
# None
# first
# 1  
# 2
# 3
# 4
# None