I am new to both OOP and data structures and would appreciate if someone could help me better understand the code below (linked list in Python). Specifically, I want to know what object type or class does "current" from append method belong to - is it Element or LinkedList? Since it is indented within LinkedList, I am inclined to believe it is a LinkedList. Second, is current.next accessing the "next" attribute of Element class? If yes, then how? Any clarity would be helpful. I have been able to follow more clearly other versions of linked list codes that would explicitly use an instance of Element class where "current" is used in this code, but I just can't seem to comprehend what is going on here.
Thank you in advance for your help
class Element(object):
def __init__(self, value):
self.value = value
self.next = None
class LinkedList(object):
def __init__(self, head=None):
self.head = head
def append(self, new_element):
current = self.head
if self.head:
while current.next:
current = current.next
current.next = new_element
else:
self.head = new_element
def get_position(self, position):
counter = 1
current = self.head
if position < 1:
return None
while current and counter <= position:
if counter == position:
return current
current = current.next
counter += 1
return None
def insert(self, new_element, position):
counter = 1
current = self.head
if position > 1:
while current and counter < position:
if counter == position - 1:
new_element.next = current.next
current.next = new_element
current = current.next
counter += 1
elif position == 1:
new_element.next = self.head
self.head = new_element
def delete(self, value):
current = self.head
previous = None
while current.value != value and current.next:
previous = current
current = current.next
if current.value == value:
if previous:
previous.next = current.next
else:
self.head = current.next
# Test cases
# Set up some Elements
e1 = Element(1)
e2 = Element(2)
e3 = Element(3)
e4 = Element(4)
# Start setting up a LinkedList
ll = LinkedList(e1)
ll.append(e2)
ll.append(e3)
# Test get_position
# Should print 3
print(ll.head.next.next.value)
# Should also print 3
print(ll.get_position(3).value)
# Test insert
ll.insert(e4,3)
# Should print 4 now
print(ll.get_position(3).value)
# Test delete
ll.delete(1)
# Should print 2 now
print(ll.get_position(1).value)
# Should print 4 now
print(ll.get_position(2).value)
# Should print 3 now
print(ll.get_position(3).value)