Preorder traversal in python: suppressing output -

i have tree exists tree object:

class tree:     ...  class node:     ...     self.branch_type='node'     self.children=[] # list of immediate children     ...  class leaf:     ...     self.branch_type='leaf'     ... 

this representation written else, i'm building on top of.

i've written preorder_traverse() function so:

def preorder_traverse(node, preorder_ls, verbose=false):     preorder_ls.append(node)     if node.branch_type == "node":         if verbose:             print(node)         preorder_traverse(node.children[0], preorder_ls)         preorder_traverse(node.children[1], preorder_ls)     elif node.branch_type == "leaf":         if verbose:             print(node, node.name) 

usage:

>>>preorder_ls = [] # init empty list filled >>>preorder_traverse(node, preorder_ls) 

this populate preorder_ls, desired, prints out objects whenever call preorder_traverse! weird because happens if set verbose false. there quirk way return works, or how recursive algorithms called in python i'm missing? i'm looking suppress output being printed screen.