Module `dalpy.queues`

This module holds classes related to FIFO queues.

This module contains Queue, an implementation of a FIFO queue, and QueueUnderflowError, an error raised by Queue.

Examples

Initializing, adding, and removing elements from a Queue:

q = Queue()
q.enqueue(1)
q.enqueue(2)
q.dequeue()

The following code will raise a QueueUnderflowError because the second dequeue is done on an empty Queue:

q.dequeue()
q.dequeue()

class Queue

This class represents a FIFO queue that has no maximum capacity.

To initialize a Queue:

q = Queue()

To add elements to the end of q:

q.enqueue(1)
q.enqueue(2)

To remove and return the element at the front of q (in this case x = 1):

x = q.dequeue()

To see the element at the front of q (in this case y = 2):

y = q.front()

Initializes an empty Queue in O(1) time.

def dequeue(self)

Removes the element at the front of this Queue.

This operation runs in O(1) time with respect to the size of this Queue.

The element at the front of the Queue that was removed. That is, the element that was first added to this Queue of the elements in it.

def enqueue(self, value)

Adds an element to the end of this Queue.

This operation runs in O(1) time with respect to the size of this Queue.

def front(self)

Gets the element at the front of this Queue.

This operation runs in O(1) time with respect to the size of this Queue.

The element at the front of the Queue. That is, the element that was first added to this Queue of the elements in it.

def is_empty(self)

Returns True if this Queue is empty, False otherwise in O(1) time w/r/t the size of this Queue.

def size(self)

Returns the integer number of elements in this Queue in O(1) time w/r/t the size of this Queue.

class QueueUnderflowError (operation)

This class is used by Queue to raise errors for operations done on an empty Queue.

Initializes a QueueUnderflowError that will be raised associated with a particular Queue operation.