simpletree3 2.0.0

SimpleNode

This is the base class that provides the tree node functionality by connecting parents to children. Additional functionality can be added by deriving from SimpleNode.

Each node is identified by a key parameter of an arbitrary hashable type. Node keys must be unique among the direct children of a node, since node children are held in a dict using the key attribute as dictionary keys (hence the hashable requirement).

Connections with nodes up and down the tree are accessed through the parent and children properties (children offers an iterator for the child nodes, sorted by node key). The root node of a tree is the node with parent equal to None. Setting the parent of a node checks that no loops are inserted and adds the current node to the parent’s children (if needed). Deleting a parent sets it to None and removes the node from the parent’s children.

Some additional convenience properties are defined - siblings, ancestors, depth, height - as well as methods for adding and removing child nodes.

FlexibleNode

This is a convenience class that add hooks to setting and deleting a parent. The motivation for providing it is that currently Python does not offer a simple syntax for calling a base class property from a derived class when that property is overriden, so by inheriting from FlexibleNode instead of SimpleNode one only has to override the hooks to perform any desired operations. Adding and deleting children can be directly overriden, since they are not implemented as properties. The design decision of having the hook functionality implemented in a separate class allows one to choose the trade-off between speed and flexibility of tree building (important for very large trees).