Circular_linked_list.py

'''
Circular linked list is circular type linked list.
which in this case track form tail.
One of the great thing that is better than simple linked list is it can access all element by roltating.
ALso it is easy to put element at front or tail or detlete front or tail(Reason :Track from tail).
'''

class CList:
    class Node:
        def __init__(self, item,nexts): # Make Node : item for storage, next linking next node 
            self.item = item
            self.next = nexts

    def __init__(self): #Starting CList initializing
        self.last = None
        self.size = 0

    def lens(self): #lens : number of items in linked list
        return self.size

    def is_empty(self): # Check if Circular list is empty
        return self.size == 0

    def insert_first(self, item): # Inserting new node to first circular list
        n = self.Node(item, None)

        if self.is_empty():
            n.next = n
            self.last=n
        else:
            n.next = self.last.next
            self.last.next = n
        self.size += 1

    def insert_last(self, item): # Inserting new node to first circular list
        n = self.Node(item, None)

        if self.is_empty():
            n.next = n
            self.last=n
        else:
            n.next = self.last.next
            self.last.next = n
            self.last = n
        self.size += 1

    def first(self): # Show first item
        if self.is_empty():
            raise EmptyError("List is empty")
        f = self.last.next
        return f.item

    def print_list(self): # Print and show the linked list
        if self.is_empty():
            print("list is empty")
        else:
            f = self.last.next
            p = f
            while p.next != f:
                print(p.item,"-> ", end="")
                p = p.next
            print(p.item)

    def delete_first(self): # Delete first node
        if self.is_empty():
            raise EmptyError("List is empty")
        x = self.last.next
        if self.size == 1:
            self.last = None
        else:
            self.last.next = x.next
        self.size -=1

    def delete_last(self): # Delete last node
        if self.is_empty():
            raise EmptyError("List is empty")
        x = self.last
        if self.size == 1:
            self.last = None
        else:
            while(x.next != self.last):
                x = x.next
            self.last = x
            self.last.next=x.next.next

        self.size -=1

            
    def search_by_name(self,name): # Search item by it`s name
        if self.is_empty():
            raise EmptyError("List is empty")
        f = self.last.next
        x = f
        count = 0
        while (x.item != name):
            if (x.next == f):
               return "There is no item with such name"
            count = count + 1
            x = x.next
        return count

class EmptyError(Exception):
    pass

if __name__=="__main__": # Test this data structure
    c = CList()
    c.insert_first("b")
    c.insert_last("c")
    c.insert_first("a")
    c.insert_last("d")
    c.print_list()
    print("Find index of node item(c) :", c.search_by_name("c"))
    print("Length of S is :",c.lens())
    print("First node of S",c.first())
    c.delete_last()
    print("Afeter deleting last node :",end="")
    c.print_list()
    print("Length of S is :",c.lens())
    print("First node of S",c.first())
    c.delete_last()
    print("Afeter deleting last node :",end="")
    c.print_list()
    c.delete_first()
    print("Afeter deleting first node :",end="")
    c.print_list()
    c.delete_first()
    print("Afeter deleting first node :",end="")
    c.print_list()