I've tried to create an implementation of a tree for comments. I want use it in Django to store comments. Please tell me how to implement it much simpler, without recursion, to find child nodes.

class commentTree(object):
def __init__(self, id, data, parentId = 0, childrens = None):
    "Represents one leaf Tree"
    self.id = id
    self.parentId = parentId
    self.title = data['title']
    self.body = data['body']
    self.childrens = []
    self.isLeaf = True if len(self.childrens) > 0 else False
    if childrens is not None:
        for children in childrens:

def addComment(self, parentId, data):
    root = 1 if self.isLeaf == False else 0
    comment = commentTree(parentId + root + len(self.childrens), data, self.id)
    if parentId == self.id:
        node = self.findById(parentId)

def getParent(self, node):
    "Gets parent node"
    if self.parent is not None:
        return self.parent

def getSize(self, node):
    "Returns size of childrens length + node"
    return len(node.childrens) + 1

def findById(self, id):
    def searchInChildren(id, childNodes):
        for children in childNodes:
            if children.id == id:
                return children
                searchInChildren(id, children)
    if id == self.id:
        return self
       result = searchInChildren(id, self.childrens)
       if result.id == id:
           return result
       else: return None

def getSiblings(self, node):
    "Get nodes that have one parent"
    nodes = []

    def getAllChildrens(self, child):
        for children in node.childrens:
            if children.isLeaf:
                getAllChildrens(self, children)

    getAllChildrens(self, node)
    return nodes
  • \$\begingroup\$ Obligatory suggestion to follow the style guide (also, please review the indentation). \$\endgroup\$ – jonrsharpe Aug 2 '14 at 18:45

A few comments regarding style:

  • As pointed out by @jonrsharpe

    • Please have a look at PEP8
    • Use for spaces for each indentation level
  • Naming

    • Use capitalized words for class names (commentTree -> CommentTree)
    • Use underscores for methods (findById -> find_by_id)
  • Do not use spaces around the equal sign to set default values for arguments (parentId = 0 -> parent_id=0)

  • Review hardcoded booleans since usually they are not needed:

    self.isLeaf = True if len(self.childrens) > 0 else False
    self.is_leaf = len(self.children) > 0  # True if ... else False not needed
    root = 1 if self.isLeaf == False else 0
    root = 1 if not self.is_leaf else 0  # False not needed
    root = int(not self.is_leaf)  # boolean to int conversion
  • Do not use builtin name functions for arguments (id)

  • Note that children is already plural

Regarding the code:

  • addComment method

    • What is the goal of the new commentTree object id calculation? Shouldn't be easier to get a new id from the database itself?
    • What is the benefit of being able to add a node as a child of a node that is not the node for which the method was called. This makes the API confusing in my opinion.
  • getParent method

    • What is the expected returned value when self.parent is None?
    • If the expected value is None, then the whole method implementation could be return self.parent
  • getSize method

    • Why is there a node parameter to this method? Shouldn't return the length of the tree object itself?
    • This method implementation should be recursive. Note that each child may have children on its own.
  • findById method

    • Why don't you like the recursive implementation? Recursion is what makes them implementation easier and I don't think you need to handle more levels than allowed by the interpreter
    • In the recursion the base case, the one for a leaf node, is missing
    • I'd try something like this:

      def find_by_id(self, comment_id):
          """Find node by id."""
          if self.node_id == node_id:
              return self
          if self.is_leaf:
              return None
          for child in self.chidren:
              node = child.find_by_id(id)
              if node:
                  return node
  • getSiblings method

    • Why is there a node parameter to this method? Shouldn't return the siblings of the current node?
    • There is no need to implement any recursion since siblings are the nodes at the same level of the tree.
    • I'd try something like this:

      def get_siblings(self):
          """Get sibling nodes."""
          # Get parent (not implemented, but using find_by_id on the root node should work)
          parent = ...
          return [node for node in parent.children if node.id != self.id]

I hope this helps.

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