Python - Count nodes in the Circular Doubly Linked List

Counting nodes in a circular doubly linked list is very useful while working on it. It requires creating a temp node pointing to the head of the list and a variable called i with initial value 0. If the temp node is not null, increase i by 1 and move to the next node using temp next. Repeat the process till the temp node reaches the head. The final value of i will be the total number of nodes in the circular doubly linked list.

The function countNodes is created for this purpose. It is a 4-step process.

```def countNodes(self):

#1. create a temp node pointing to head

#2. create a variable to count nodes
i = 0

#3. if the temp node is not null increase
#   i by 1 and move to the next node, repeat
#   the process till the temp becomes null
if (temp != None):
i += 1
temp = temp.next
i += 1
temp = temp.next

#4. return the count
return i
```

The below is a complete program that uses above discussed concept of counting the total number of nodes of a circular doubly linked list.

```# node structure
class Node:
def __init__(self, data):
self.data = data
self.next = None
self.prev = None

def __init__(self):

#Add new element at the end of the list
def push_back(self, newElement):
newNode = Node(newElement)
return
else:
temp = temp.next
temp.next = newNode
newNode.prev = temp

#count nodes in the list
def countNodes(self):
i = 0
if (temp != None):
i += 1
temp = temp.next
i += 1
temp = temp.next
return i

#display the content of the list
def PrintList(self):
if(temp != None):
print("The list contains:", end=" ")
while (True):
print(temp.data, end=" ")
temp = temp.next
break
print()
else:
print("The list is empty.")

# test the code

#Add four elements in the list.
MyList.push_back(10)
MyList.push_back(20)
MyList.push_back(30)
MyList.push_back(40)

#Display the content of the list.
MyList.PrintList()

#number of nodes in the list
print("No. of nodes: ", MyList.countNodes())
```

The above code will give the following output:

```The list contains: 10 20 30 40
No. of nodes: 4
```

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