Linked List Nodes in Python

Question

I am working on linked list python code (see code below), and I can't for the life of me work out why when the condition check_value == search_term is clearly True the function does not return that.

https://i.sstatic.net/2hpmp.jpg

You can see that the print statement for the fifth iteration shows that the statement is True, but the function overall evaluates to False. Can anyone explain what I am doing wrong?

class LinkedListNode:
def __init__(self, value, next_node = None):
    self.value = value
    self.next_node = next_node

def linked_list_search(node, search_term):
    check_value = node.value
    next_node = node.next_node
    
    if not next_node == None:
        next_node_value = next_node.value
        
        if check_value == search_term:
            return True
        else:
            
            linked_list_search(node.next_node, search_term)
    
    if check_value == search_term:
        
        return True
    
    
    return False

#Below are lines of code that create a linked list,
#and then search for two values in that linked list:
#one that is there, one that isn't. If your function
#works, it should print True then False.
node_7 = LinkedListNode(5)
node_6 = LinkedListNode(2, node_7)
node_5 = LinkedListNode(9, node_6)
node_4 = LinkedListNode(1, node_5)
node_3 = LinkedListNode(4, node_4)
node_2 = LinkedListNode(6, node_3)
root_node = LinkedListNode(7, node_2)

print(linked_list_search(root_node, 9))
print(linked_list_search(root_node, 3))

Thanks in advance.

Update: Apologies for original post. I wanted to show the output, which is why I included an image. Code is now included.

Thank you for the replies.

You have written a recursive code and you are missing one of the base condition also else part should also have return statement as John Coleman mentioned in the comment. That's why overall response is False and result will be always unpredictable. Post a minimal code instead of image, then you will get response faster :). — Deepak Singh
– Deepak Singh, Commented Jul 24, 2021 at 11:36
I think it should be OK now (hopefully). Thanks to your advice, it now works. Apologies again for the original post. Thank you very much. — Rolen44
– Rolen44, Commented Jul 24, 2021 at 12:06
It still doesn't work. It is missing the class definition now and the body of the function isn't indented. — John Coleman
– John Coleman, Commented Jul 24, 2021 at 12:10

Shravan40 · Accepted Answer · 2021-07-24 12:08:12Z

1

You can implement the linked_list_search in a lot simpler way.

def linked_list_search(node, search_term):
    # Iterate through list till you reach the tail of the list
    while(node):
        if(node.value == search_term):
            # Return True as soon as you find the search_term
            return True
        # Assign node to the next node in the list 
        node = node.next
    # Return False if search_term not found in the linked_list
    return False

answered Jul 24, 2021 at 12:08

Shravan40

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