imageList.py

# circularLinkedList.py
# A limited implementation of a circular singly-linked list 
# Created 2/24/2017 by Connor Dale

class Node:
    # A Node class that holds data and a pointer to the next node in the linked list

    def __init__(self,data,next):
        '''
        Creates a Node object
        Inputs:
            data ------ the information stored in the node
            next ------ the next node in the list
        Outputs:
            None
        '''
        self.data = data
        self.next = next
        __slots__ = [self.data, self.next]


class CircularLinkedList:
    # A circular linked list class that stores data as a chain of Node objects
    
    def __init__(self):
        '''
        Creates a CircularLinkedList object
        Inputs:
            None
        Outputs:
            None
        '''
        self.last = None  # the last node in the list
        self.current = None # the current player


    def append(self,data):
        '''
        Adds a node with the given data to the end of the list
        Inputs:
            data --------- the information to be stored
        Outputs:
            None
        '''
        new_node = Node(data,None)  # node to be added

        if self.is_empty():
            self.last = new_node
            new_node.next = new_node
        else:
            new_node.next = self.last.next  # new node links to first node
            self.last.next = new_node  # previous last node links to new node
            self.last = new_node  # new node gets last-node pointer 


    def set_current(self,data=None):
        '''
        Searches the list for a node containing the specified value, then 
        sets the current player marker
        Inputs:
            data --------- the value in the list that is searched for
        Outputs:
            None
        '''
        if not self.is_empty():
            if data == None:
                self.current = self.last
                return
            marker = self.last
            while True:
                marker = marker.next
                if marker.data == data:
                    self.current = marker
                if marker == self.last:
                    return


    def update_current(self):
        '''
        Sets the current player marker to the next in the list
        Inputs:
            None
        Outputs:
            None
        '''
        if self.current != None:
            self.current = self.current.next


    def is_empty(self):
            '''
            Checks whether there is a value assigned to self.last
            to determine whether there are any elements in the list
            Inputs:
                None
            Outputs:
                True ------ if list is empty
                False ----- if it isn't
            '''
            if self.last == None:
                return True
            return False