python array as queue code example

Example 1: python list as queue

# Demonstrate queue implementation using list
 
# Initializing a queue
queue = []
 
# Adding elements to the queue
queue.append('a')
queue.append('b')
print(queue)
 
# Removing elements from the queue
print("\nElements dequeued from queue")
print(queue.pop(0))
print(queue.pop(0))
 
print("\nQueue after removing elements")
print(queue)
 
# print(queue.pop(0)) will raise and IndexError as the queue is now empty

Example 2: queue with array python

class ArrayQueue:
	def __init__(self):
		self._data = []
		self._size = 0
		self._front = 0

	def __len__(self):
		return self._size()

	def is_empty(self):
		return self._size == 0

	def enqueue(self, e):
		self._data.append(e)
		self._size = self._size + 1

	def deque(self):
		if self.is_empty():
			raise Empty('queue is empty')
		else:
			value = self._data[self._front]
			self._data[self._front] = None
			self._front = self._front + 1
			self._size = self._size - 1
			return value

	def first(self):
		if self.is_empty():
			raise Empty('queue is empty')
		else:
			return self._data[self._front]
 

class Empty(Exception):
	pass