arrayqueue.py

# Implementation of the Queue ADT using a circular array.
from myarray import myArray

class Queue:
    # Creates an empty queue.
    def __init__( self, maxSize ):
        self._count = 0
        self._front = 0
        self._back = maxSize - 1
        self._qArray = myArray( maxSize )

    # Returns True if the  queue is empty
    def isEmpty( self ):
        return self._count == 0

    # Returns True if the queue is full.
    def isFull( self ):
        return self._count == len( self._qArray )

    # Returns the number of items in the queue.
    def __len__( self ):
        return self._count

    # Adds the given item to the queue.
    def enqueue( self, item ):
        assert not self.isFull(), "Cannot enqueue to a full queue."
        maxSize = len( self._qArray )
        self._back = ( self._back + 1 ) % maxSize
        self._qArray[ self._back ] = item
        self._count += 1

    # Removes and returns the first item in the queue.
    def dequeue( self ):
        assert not self.isEmpty(), "Cannot dequeue from an empty queue."
        item = self._qArray[ self._front ]
        maxSize = len( self._qArray )
        self._front = ( self._front + 1 ) % maxSize
        self._count -= 1
        return item

if __name__ == '__main__':
    Q = Queue( 5 )
    Q.enqueue( 28 )
    Q.enqueue( 19 )
    Q.enqueue( 45 )
    Q.enqueue( 13 )
    Q.enqueue( 7 )

    for i in range( len(Q) ):
        cur_item = Q.dequeue()
        print cur_item,
    print ''