"""
Tree data structure
===================
TreeNode is a generic class which can carry arbitrary python objects. It comes with basic methods to
set parent and children. A method `map` allows to apply functions recursively on the tree in a
generic manner.
"""
from __future__ import annotations
from typing import Callable, Generic, Iterable, Iterator, Sequence, TypeVar
# pylint: disable=invalid-name
T = TypeVar("T")
V = TypeVar("V")
# TypeVar used in methods that return an object of the same type as `self` (also for subclasses of
# `TreeNode`).
Self = TypeVar("Self", bound="TreeNode")
NodeType = TypeVar("NodeType", bound="TreeNode")
[docs]def PreOrderTraversal(tree_node: NodeType) -> Iterator[NodeType]:
"""Iterate on a tree in a pre-order traversal fashion"""
stack = [tree_node]
while stack:
node = stack.pop()
yield node
stack.extend(node.children[::-1])
[docs]def DepthFirstTraversal(tree_node: NodeType) -> Iterable[NodeType]:
"""Iterate on a tree in a post-order traversal fashion"""
seen: set[NodeType] = set()
def _inner(node: NodeType) -> Iterable[NodeType]:
if node in seen:
return
seen.add(node)
for child in node.children:
yield from _inner(child)
yield node
return _inner(tree_node)
[docs]class TreeNode(Generic[T], Iterable[T]):
r"""Tree node data structure
Nodes have an attribute item to carry arbitrary information. A node may only have one parent
and can have as many children as desired.
Parents can be set at initialization or via `node.set_parent`. Setting a parent automatically
set the current node as the child of the parent.
Children can be set at initialization or via `node.add_children`. Setting children
automatically set their parent as the current node.
Tree of nodes are iterable, by default with preorder traversal.
.. seealso::
`orion.core.utils.tree.PreOrderTraversal`
`orion.core.utils.tree.DepthFirstTraversal`
Attributes
----------
item: T
Can be anything
parent: None or instance of `orion.core.utils.tree.TreeNode`
The parent of the current node, None if the current node is the root.
children: None or list of instances of `orion.core.utils.tree.TreeNode`
The children of the current node.
root: instance of `orion.core.utils.tree.TreeNode`
The top node of the current tree. The root node returns itself.
Examples
--------
.. code-block:: python
:linenos:
a = TreeNode("a")
b = TreeNode("b", a)
c = TreeNode("c", a)
d = TreeNode("d", a)
e = TreeNode("e", a)
f = TreeNode("f", b)
g = TreeNode("g", b)
h = TreeNode("h", e)
# Gives this tree
# a
# | \ \ \
# b c d e
# | \ |
# f g h
g.set_parent(e)
# Gives this tree
# a
# | \ \ \
# b c d e
# | | \
# f h g
c.add_children(h, g)
# Gives this tree
# a
# | \ \ \
# b c d e
# | | \
# f h g
a.drop_children(c)
# Gives this tree
# a
# | \ \
# b d e
# |
# f
"""
__slots__ = ("_item", "_parent", "_children")
def __init__(
self: Self,
item: T,
parent: Self | None = None,
children: Sequence[Self] = tuple(),
):
"""Initialize node with item, parent and children
.. seealso::
:class:`orion.core.utils.tree.TreeNode` for information about the attributes
"""
self._item: T = item
self._parent: Self | None = None
self._children: list[Self] = []
if parent is not None:
self.set_parent(parent)
if children:
self.add_children(*children)
@property
def item(self) -> T:
"""Get item of the node which may contain arbitrary objects"""
return self._item
@item.setter
def item(self, new_item: T) -> None:
"""Set item of the node with arbitrary objects"""
self._item = new_item
@property
def parent(self: Self) -> Self | None:
"""Get parent of the node, None if no parent"""
return self._parent
[docs] def drop_parent(self) -> None:
"""Drop the parent of the node, do nothing if no parent
Note that the node will be removed from the children of the parent as well
"""
if self.parent is not None:
assert self._parent is not None
self._parent.drop_children(self)
[docs] def set_parent(self: Self, node: Self) -> None:
"""Set the parent of the node
Note that setting a new parent will have the effect of dropping the previous parent, hence
dropping this current node from the previous parent's children list.
.. seealso::
`orion.core.utils.tree.TreeNode.drop_parent`
"""
if node is self.parent:
return
if node is not None and not isinstance(node, TreeNode):
raise TypeError(f"Cannot set parent to {str(node)}")
if self.parent is not None:
self.drop_parent()
if node is not None:
node.add_children(self)
@property
def children(self: Self) -> list[Self]:
"""Get children of the node, empty list if no children"""
return self._children
[docs] def drop_children(self: Self, *nodes: Self) -> None:
"""Drop the children of the node, do nothing if no parent
If no nodes are passed, the method will drop all the children of the current node.
Note that the parent of the given node will be removed as well
Raises
------
ValueError
If one of the given nodes is not a children of the current node.
"""
if not nodes:
nodes = tuple(self.children)
for child in list(nodes):
del self._children[self._children.index(child)]
# pylint: disable=protected-access
child._parent = None
[docs] def add_children(self: Self, *nodes: Self) -> None:
"""Add children to the current node
Note that added children will have their parent set to the current node as well.
.. seealso::
`orion.core.utils.tree.TreeNode.drop_children`
"""
for child in nodes:
if child is not None and not isinstance(child, TreeNode):
raise TypeError(f"Cannot add {child} to children")
if child not in self._children:
# TreeNode.set_parent uses add_children so using it here could cause an infinite
# recursion. add_children() gets the dirty job done.
child.drop_parent()
# pylint: disable=protected-access
child._parent = self
self._children.append(child)
@property
def root(self) -> TreeNode[T]:
"""Get the root of the tree
Root node returns itself
"""
if self.parent is None:
return self
return self.parent.root
@property
def leafs(self: Self) -> list[Self]:
"""Get the leafs of the tree"""
leaves: list[Self] = []
for child in self.children:
leaves += child.leafs
if not leaves:
return [self]
return leaves
@property
def node_depth(self) -> int:
"""The depth of the node in the tree with respect to the root node."""
if self.parent:
return self.parent.node_depth + 1
return 0
[docs] def get_nodes_at_depth(self: Self, depth: int) -> list[Self]:
"""Returns a list of nodes at the corresponding depth.
Depth is relative to current node. To get nodes at a depth relative
to the root, use ``node.root.get_nodes_at_depth(depth)``.
"""
def has_depth(
node: TreeNode[T], children: Sequence[TreeNode[T]]
) -> tuple[Sequence[TreeNode[T]], Sequence[TreeNode[T]] | None]:
if node.node_depth - self.node_depth == depth:
return [node], None
return [], children
nodes = self.map(has_depth, self.children)
return sum((node.item for node in nodes), [])
# NOTE: Would be nice to type-annotate this method with overloads, but it's really tough.
[docs] def map(
self,
function: Callable,
node: TreeNode[T] | Sequence[TreeNode[T]] | None,
) -> TreeNode:
r"""Apply a function recursively on the tree
The function can be applied upwards on parents or downwards on children. The direction is
defined by passing self.parent or self.children as the node argument.
Parameters
----------
function : callable
Callable object to which will be passed the current node plus the parent node or the
children nodes, depending on the direction of function application.
If map on parents, callable(self, rval_parent_node)
If map on children, callable(self, rval_children_nodes).
Note that the callable object is expected to return an object which will be set as the
current node's item (in the resulting tree), and the parent node or the children nodes
depending on the direction of function application.
node: None, `orion.core.evc.TreeNode` or list
Can be either
`None`: function is applied on current node only
`self.parent`: function is applied recursively climbing up the tree until the root
`self.children`: function is applied recursively going down the tree until the leafs
Examples
--------
.. code-block:: python
:linenos:
# Tree structure
# a
# | \ \ \
# b c d e
# | \ |
# f g h
#
root = TreeNode(1)
b = TreeNode(1, root)
TreeNode(1, root)
TreeNode(1, root)
e = TreeNode(1, root)
f = TreeNode(1, b)
TreeNode(1, b)
h = TreeNode(1, e)
def increment(node, children):
for child in TreeNode(0, None, children):
child.item += 1
return node.item + 1, children
# Should return
#
# 2
# | \ \ \
# 3 3 3 3
# | \ |
# 4 4 4
rval = root.map(increment, root.children)
assert [node.item for node in rval] == [2, 3, 4, 4, 3, 3, 3, 4]
def increment_parent(node, parent):
if parent is not None:
for parent in parent.root:
parent.item += 1
return node.item + 1, parent
# Should return
#
# 4
# |
# 3
# |
# 2
rval = f.map(increment_parent, f.parent)
assert [node.item for node in rval.root] == [4, 3, 2]
rval = h.map(increment_parent, h.parent)
assert [node.item for node in rval.root] == [4, 3, 2]
"""
if node is None:
rval, _ = function(self, None)
return TreeNode(rval)
elif node is self.parent:
assert node is not None
assert isinstance(node, TreeNode)
rval_parent_node = node.map(function, node.parent)
rval, parent_node = function(self, rval_parent_node)
return TreeNode(rval, parent_node)
elif node is self.children:
rval_children_nodes = [
child.map(function, child.children) for child in self.children
]
rval, children_nodes = function(self, rval_children_nodes)
return TreeNode(rval, parent=None, children=children_nodes)
else:
raise ValueError(f"Invalid nodes: {str(node)}")
def __iter__(self: Self) -> PreOrderTraversal[Self]:
"""Iterate on the tree with pre-order traversal"""
return PreOrderTraversal(self)
def __repr__(self) -> str:
"""Represent the object as a string."""
parent_item = self.parent.item if self.parent is not None else None
children = [child.item for child in self.children]
return f"{self.__class__.__name__}({self.item}, parent={parent_item}, children={children})"
[docs]def flattened(trials_tree: TreeNode[T]) -> list[T]:
"""Get a list of the tree items in pre-order traversal"""
return [node.item for node in trials_tree]