Self-referencing classes in python?

Question

In Python, can you have classes with members that are themselves pointers to members of the type of the same class? For example, in C, you might have the following class for a node in a binary tree:

struct node {
    int data;
    struct node* left;
    struct node* right;
} 

How would you equivalently create this in python?

Answer 1

Python is a dynamic language. Attributes can be bound at (almost) any time with any type. Therefore, the problem you are describing does not exist in Python.

Answer 2

Emulating a C struct in Python (using str instead of int as the data type):

"Declaration":

class Node(object):
    data = None # str
    left = None # Node object or None
    right = None # Node object or None

Usage:

root = Node()
root.data = "foo"

b = Node()
b.data = "bar"
root.left = b

z = Node()
z.data = "zot"
root.right = z

Answer 3

http://code.activestate.com/recipes/286239-binary-ordered-tree/ is a sample binary tree created using that structure.

Answer 4

How would I equivalently create this in python?

class node( object ):
    def __init__( self, data, left, right ):
        self.data = data
        self.left = left
        self.right = right

Since all Python variables are, in effect, typeless references, you don't have to mention up front that left and right are going to be instances of nodes.

Answer 5

You can't declare types in Python - therefore, there are no problems declaring types in Python.