Recursive method doesn't return a value

Question

I am building a program to build and explore binary trees in native Python. I defined a Node class and a depth() method which aims to get the depth of the given node recursively. This works as expected when I want to print the depth, but it returns None

class Node():
    def __init__(self, n, g=None, d=None, parent=None):
        self.parent = parent
        self.n = n
        self.g = g
        self.d = d

    def addNodes(self, g=None, d=None):
        # some code to add nodes

    def printTree(self, indent = "") :
        # some code to pretty print the tree

    def depth(self, count=0):
        if self.parent != None :
            count += 1
            self.parent.depth(count)
        else :
            print(f"Printing count inside the function : {count}")
            return count

def treeExemple():
    # creating a simple tree
    root = Node("root")
    a, b = root.addNodes("a", "b")
    c, d = a.addNodes("c", "d")
    e, f = b.addNodes("e", "f")
    i = e.addNodes(d="i")
    j, k = f.addNodes("j", "k")

    # printing it to check everything is right
    root.printTree()

    # trying to print the depth of a particular node
    depthK = k.depth()
    print(f"Printing count outside the function : {depthK}")

if __name__ == '__main__':
    treeExemple()

Running the program :

+-root
|  +-a
|  |  +-c
|  |  +-d
|  +-b
|  |  +-e
|  |  |  +-i
|  |  +-f
|  |  |  +-j
|  |  |  +-k
Printing count inside the function : 3
Printing count outside the function : None

Since it's the first time I dive into oop, I might be missing something really obvious. Any help will be greatly appreciated !

`return self.parent.depth(count)` – Patrick Artner Sep 13 '20 at 12:35 — Patrick Artner, Sep 13 '20 at 12:35

score 2 · Accepted Answer · answered Sep 13 '20 at 12:37

In the depth function, you need to return the value self.parent.depth(count) inside the first if.

    def depth(self, count=0):
        if self.parent != None :
            count += 1
            return self.parent.depth(count)
        else :
            print(f"Printing count inside the function : {count}")
            return count

Recursive method doesn't return a value

1 Answers1