How are these while loops being used?

[thefatron]

Very new to programming and simply dont understand how this while loop is being used? Is the itr=itr.next the condition that needs to be maintained? I cant find any examples where there isnt a condition with the while statement.


while itr:
llstr += str(itr.data) + '-->'
itr = itr.next

class Node:
    def __init__(self, data=None, next= None):
        self.data = data
        self.next = next

class linkedlist:
    def __init__(self):
       self.head = None

    def insert_at_beginning(self, data):
         node = Node(data, self.head)
         self.head = node

    def print(self):
        if self.head is None:
            print("Linked List is empty")
            return

        itr = self.head
        llstr = ''

        while itr:
            llstr += str(itr.data) + '-->'
            itr = itr.next

        print(llstr)