CODEWITHSUNDEEP
classobjectpython-3.xlinked-list
user3019849
user3019849

Reputation: 15

Python3 objects passing from functions

The below code snippet is for deleting a node in linked list. My class contains two members namely data and next a pointer to hold other objects of that class type. When, I run my program, I don't get any error. If I try to delete the first item in the linked list, it enters the First for loop and displays the message "The data is found". But if I print my list, I am seeing the element in the list. I think this is because of assigning objects back, but I am not able to find where I have done that mistake. Any help is greatly appreciated.

def deleteNode(self, a_data):
        flag = 0


        if (self.data == a_data):
            print("The data is found")
            self = self.next
            flag = 1

        else:

            while(self.next != None):

                if (self.next.data == a_data):

                    self.next = self.next.next
                    flag = 1
                    break

                else:

                    self = self.next

        if(flag):
            print("Data Deleted")
        else:
            print("Data not available")

Thanks

Upvotes: 1

Views: 49

Answers (2)

jfs
jfs

Reputation: 414645

self = self.next in your code has no effect on the outside world: it just assigns to a local variable.

It looks like you are trying to delete a node from within Node class itself. You could use a function instead that accepts a list head and returns a (possibly new) list head with the corresponding item deleted:

def delete_node(head, data):
    """Delete the first node in the `head` list that has `data`."""
    prev, node = None, head
    while node is not None: # until the last node (`None` means empty list)
        if node.data == data: # found node that has data
           if prev is None: # we are at the very beginning of the list
              assert head is node
              head = node.next # remove the first node
           else:
              assert prev.next is node
              prev.next = node.next # remove internal node
           break
        prev, node = node, node.next
    return head

Upvotes: 1

user3019849
user3019849

Reputation: 15

Friends,

I modified my function. I think the error may be because not assigning back the value to the original one, so I made my function to return value. Comments and other methods and any other reason for above than mine are cordially welcome.

def deleteNode(self, a_data):
        flag = 0


        if (self.data == a_data):
            print("The data is found")
            self = self.next
            flag = 1

        else:

            while(self.next != None):

                if (self.next.data == a_data):

                    self.next = self.next.next
                    flag = 1
                    break

                else:

                    self = self.next

        if(flag):
            print("Data Deleted")
        else:
            print("Data not available")

        return self

Thanks S

Upvotes: 0

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