trees Module

Data structures for representing trees.

@author: drusk

class pml.supervised.decision_trees.trees.Node(value)

A node in a tree. Holds a value and may have branches connecting it to other nodes.

__init__(value)

Constructs a new node.

Args:

value:

The data value to be associated with this node.

add_child(branch, child)

Creates a branch from this node to another node which will be the child.

Args:

branch:

The identifier for the branch connecting this node to the child node.

child: Node

Another node which will be a child of the current node.

Returns:

void

get_all_descendants()

Retrieves all descendants of the current node, i.e. nodes which can eventually be reached by following outgoing branches from the current node.

Returns:

descendants: list(Node)

get_branches()

Retrieves all the branches to children of the current node.

Returns:

branches: list

A list of all the branches to child nodes. Note that this means branches TO this node are not included.

get_child(branch)

Retrieves the child node connected by the specified branch.

Args:

branch:

The identifier that was used to associate a child node with the current node.

Returns:

child: Node

The child node found by following the specified branch.

Raises:

KeyError if the specified branch does not exist.

get_height()

Determines the node’s height, i.e. the maximum number of edges between it and a leaf node.

Returns:

height: int

get_value()

Retrieves the data value associated with this node.

Returns:

value:

The value associated with this node.

is_leaf()

Checks if this node is a leaf (has no children).

Returns:

is_leaf: boolean

True if this node has no children.

class pml.supervised.decision_trees.trees.Tree(root_node)

A tree containing nodes which are connected to each other by directed edges.

__init__(root_node)

Constructs a new tree.

Args:

root_node: Node

The node which will be at the root of the tree.

get_depth()

Calculates the number of nodes on the longest path from root to leaf.

Returns:

depth: int

get_leaves()

Retrieves all leaf nodes from the tree.

Returns:

leaves: list(Node)

get_num_leaves()

Counts the number of leaves in the tree.

Returns:

num_leaves: int

get_root_node()

Retrieves the root node of the tree. This node will have only outgoing edges (children), no incoming edges (parents).

Returns:

root: Node

The root node.