From bf37e2dab8c15533883e1e51635e8b28cc78d11b Mon Sep 17 00:00:00 2001
From: Licini <leochen1990@gmail.com>
Date: Tue, 18 Jul 2023 18:01:27 +0200
Subject: [PATCH 01/14] Tree classes

---
 src/compas/datastructures/tree/__init__.py |  0
 src/compas/datastructures/tree/tree.py     | 76 ++++++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 src/compas/datastructures/tree/__init__.py
 create mode 100644 src/compas/datastructures/tree/tree.py

diff --git a/src/compas/datastructures/tree/__init__.py b/src/compas/datastructures/tree/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
new file mode 100644
index 00000000000..c8cc4c74898
--- /dev/null
+++ b/src/compas/datastructures/tree/tree.py
@@ -0,0 +1,76 @@
+from __future__ import print_function
+from __future__ import absolute_import
+from __future__ import division
+
+from compas.data import Data
+from compas.datastructures import Graph
+
+
+class TreeNode(Data):
+
+    JSONSCHEMA = {}
+
+    def __init__(self, tree):
+        super(TreeNode, self).__init__()
+        self._tree = tree
+        self._attributes = {}
+        self._parent = None
+
+    @property
+    def tree(self):
+        return self._tree
+
+    @property
+    def attributes(self):
+        return self._attributes
+
+    @property
+    def parent(self):
+        return self._parent
+    
+    @parent.setter
+    def parent(self, node):
+        assert node is None or isinstance(node, TreeNode)
+        self._parent = node
+
+    @property
+    def children(self):
+        pass
+
+    @property
+    def acestors(self):
+        pass
+
+    @property
+    def descendants(self):
+        pass
+
+    def add_child(self, node):
+        node._parent = self
+
+
+
+class Tree(Graph):
+
+    JSONSCHEMA = {}
+
+    def __init__(self):
+        super(Tree, self).__init__()
+        self._attributes = {}
+        assert self.is_valid
+    
+    @property
+    def is_valid(self):
+        pass
+
+    @property
+    def attributes(self):
+        return self._attributes
+
+    @property
+    def root(self):
+        pass
+
+    @property
+    def leaves(self):
+        pass
\ No newline at end of file

From 916f8088f11451dd294a4472fc62e9a5e3713ac2 Mon Sep 17 00:00:00 2001
From: Licini <leochen1990@gmail.com>
Date: Thu, 20 Jul 2023 15:26:37 +0200
Subject: [PATCH 02/14] more apis

---
 src/compas/datastructures/tree/tree.py | 155 +++++++++++++++++++------
 1 file changed, 122 insertions(+), 33 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index c8cc4c74898..f4549a626f8 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -1,76 +1,165 @@
 from __future__ import print_function
 from __future__ import absolute_import
 from __future__ import division
+from __future__ import annotations
 
 from compas.data import Data
-from compas.datastructures import Graph
+from compas.datastructures import Datastructure
 
 
 class TreeNode(Data):
-
     JSONSCHEMA = {}
 
-    def __init__(self, tree):
-        super(TreeNode, self).__init__()
-        self._tree = tree
-        self._attributes = {}
+    def __init__(self, name: str = None, attributes: dict = None):
+        super(TreeNode, self).__init__(name=name)
+        self.attributes = attributes or {}
         self._parent = None
+        self._children = set()
+
+    def __repr__(self) -> str:
+        return "TreeNode({})".format(self.name)
+
+    @property
+    def data(self):
+        return {
+            "name": self.name,
+            "attributes": self.attributes,
+            "parent": str(self.parent.guid) if self.parent else None,
+            "children": [str(child.guid) for child in self.children],
+        }
 
     @property
-    def tree(self):
-        return self._tree
+    def is_root(self):
+        return self._parent is None
 
     @property
-    def attributes(self):
-        return self._attributes
+    def is_leaf(self):
+        return not self._children
+
+    @property
+    def is_branch(self):
+        return not self.is_root and not self.is_leaf
 
     @property
     def parent(self):
         return self._parent
-    
-    @parent.setter
-    def parent(self, node):
-        assert node is None or isinstance(node, TreeNode)
-        self._parent = node
 
     @property
     def children(self):
-        pass
+        return list(self._children)
+
+    def add(self, node: TreeNode):
+        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        self._children.add(node)
+        node._parent = self
+
+    @property
+    def remove(self, node: TreeNode):
+        self._children.remove(node)
+        node._parent = None
 
     @property
     def acestors(self):
-        pass
+        this = self
+        while this:
+            yield this
+            this = this.parent
 
     @property
     def descendants(self):
-        pass
-
-    def add_child(self, node):
-        node._parent = self
+        for child in self.children:
+            yield child
+            for descendant in child.descendants:
+                yield descendant
 
+    def traverse(self):
+        yield self
+        for descendant in self.descendants:
+            yield descendant
 
 
-class Tree(Graph):
-
+class Tree(Datastructure):
     JSONSCHEMA = {}
 
     def __init__(self):
         super(Tree, self).__init__()
-        self._attributes = {}
-        assert self.is_valid
-    
-    @property
-    def is_valid(self):
-        pass
+        self.attributes = {}
+        self._root = None
 
     @property
-    def attributes(self):
-        return self._attributes
+    def data(self):
+        return {
+            "root": str(self.root.guid) if self.root else None,
+            "nodes": [node.data for node in self.nodes],
+        }
 
     @property
     def root(self):
-        pass
+        return self._root
+
+    def add_root(self, node: TreeNode):
+        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        if not node.is_root:
+            raise ValueError("The node is already part of another tree.")
+        self._root = node
+
+    def add(self, node: TreeNode, parent: TreeNode):
+        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        if self.root is None:
+            raise ValueError("The tree has no root node, use add_root() first.")
+        else:
+            parent.add(node)
+
+    @property
+    def nodes(self):
+        return list(self.root.traverse())
+
+    def remove(self, node: TreeNode):
+        if node.is_root:
+            self._root = None
+        else:
+            node.parent.remove(node)
 
     @property
     def leaves(self):
-        pass
\ No newline at end of file
+        for node in self.nodes:
+            if node.is_leaf:
+                yield node
+
+    def summary(self):
+        nodes = len(self.nodes)
+        branches = sum(1 for node in self.nodes if node.is_branch)
+        leaves = sum(1 for node in self.nodes if node.is_leaf)
+        print("Tree with {} nodes, {} branches, and {} leaves".format(nodes, branches, leaves))
+
+    def print(self):
+        def _print(node, depth=0):
+            print("  " * depth + str(node))
+            for child in node.children:
+                _print(child, depth + 1)
+
+        _print(self.root)
+
+
+if __name__ == "__main__":
+    from compas.data import json_dumps
+
+    R = TreeNode("R")
+    B = TreeNode("B")
+    L = TreeNode("L")
+    L2 = TreeNode("L2")
+
+    T = Tree()
+    T.add_root(R)
+
+    # T.add(B, R)
+    # T.add(L, B)
+    # T.add(L2, B)
+
+    R.add(B)
+    B.add(L)
+    B.add(L2)
+
+    # T.print()
+
+    print(json_dumps(T, pretty=True))

From a16d86fb568847050763adcdad9e790a2c84347e Mon Sep 17 00:00:00 2001
From: Licini <leochen1990@gmail.com>
Date: Fri, 21 Jul 2023 16:46:35 +0200
Subject: [PATCH 03/14] Docs

---
 CHANGELOG.md                           |   1 +
 src/compas/datastructures/__init__.py  |   5 +
 src/compas/datastructures/tree/tree.py | 198 ++++++++++++++++++-------
 3 files changed, 152 insertions(+), 52 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 643bc6867b0..abe25970f89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -62,6 +62,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Added `compas.geometry.trimesh_descent_numpy`.
 * Added `compas.geometry.trimesh_gradient_numpy`.
 * Added a deprecation warning when using `Artist` for `Plotter`.
+* Added `compas.datastructures.Tree` and `compas.datastructures.TreeNode` classes.
 
 ### Changed
 
diff --git a/src/compas/datastructures/__init__.py b/src/compas/datastructures/__init__.py
index 32a084d67b2..3fa51ddfb7c 100644
--- a/src/compas/datastructures/__init__.py
+++ b/src/compas/datastructures/__init__.py
@@ -157,6 +157,8 @@
 from .assembly.assembly import Assembly
 from .assembly.part import Feature, GeometricFeature, ParametricFeature, Part
 
+from .tree.tree import Tree, TreeNode
+
 BaseNetwork = Network
 BaseMesh = Mesh
 BaseVolMesh = VolMesh
@@ -274,6 +276,9 @@
     "Feature",
     "GeometricFeature",
     "ParametricFeature",
+    # Trees
+    "Tree",
+    "TreeNode",
 ]
 
 if not compas.IPY:
diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index f4549a626f8..150da33b667 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -3,30 +3,53 @@
 from __future__ import division
 from __future__ import annotations
 
-from compas.data import Data
 from compas.datastructures import Datastructure
 
 
-class TreeNode(Data):
-    JSONSCHEMA = {}
+class TreeNode(object):
+    """A node of a tree data structure.
+
+    Parameters
+    ----------
+    name: str, optional
+        The name of the tree ndoe.
+    attributes: dict[str, Any], optional
+        User-defined attributes of the datastructure.
+
+    Attributes
+    ----------
+    name: str
+        The name of the datastructure.
+    attributes : dict[str, Any]
+        User-defined attributes of the datastructure.
+    parent: :class:`~compas.datastructures.TreeNode`
+        The parent node of the tree node.
+    children: set[:class:`~compas.datastructures.TreeNode`]
+        The children of the tree node.
+    tree: :class:`~compas.datastructures.Tree`
+        The tree the node belongs to.
+    is_root: bool
+        True if the node is the root node of the tree.
+    is_leaf: bool
+        True if the node is a leaf node of the tree.
+    is_branch: bool
+        True if the node is a branch node of the tree.
+    acestors: generator[:class:`~compas.datastructures.TreeNode`]
+        A generator of the acestors of the tree node.
+    descendants: generator[:class:`~compas.datastructures.TreeNode`]
+        A generator of the descendants of the tree node.
+
+    """
 
     def __init__(self, name: str = None, attributes: dict = None):
-        super(TreeNode, self).__init__(name=name)
+        self.name = name
         self.attributes = attributes or {}
         self._parent = None
         self._children = set()
+        self._tree = None
 
     def __repr__(self) -> str:
-        return "TreeNode({})".format(self.name)
-
-    @property
-    def data(self):
-        return {
-            "name": self.name,
-            "attributes": self.attributes,
-            "parent": str(self.parent.guid) if self.parent else None,
-            "children": [str(child.guid) for child in self.children],
-        }
+        return "<TreeNode {}>".format(self.name)
 
     @property
     def is_root(self):
@@ -46,17 +69,29 @@ def parent(self):
 
     @property
     def children(self):
-        return list(self._children)
+        return self._children
+
+    @property
+    def tree(self):
+        return self._tree
 
     def add(self, node: TreeNode):
-        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        """Add a child node to this node."""
+        if not isinstance(node, TreeNode):
+            raise TypeError("The node is not a TreeNode object.")
         self._children.add(node)
         node._parent = self
+        node._tree = self.tree
+        if self.tree:
+            self.tree.nodes.add(node)
 
-    @property
     def remove(self, node: TreeNode):
+        """Remove a child node from this node."""
         self._children.remove(node)
         node._parent = None
+        node._tree = None
+        if self.tree:
+            self.tree.nodes.remove(node)
 
     @property
     def acestors(self):
@@ -73,38 +108,112 @@ def descendants(self):
                 yield descendant
 
     def traverse(self):
+        """Traverse the tree from this node."""
         yield self
         for descendant in self.descendants:
             yield descendant
 
 
 class Tree(Datastructure):
+    """A tree data structure.
+
+    Parameters
+    ----------
+    name: str, optional
+        The name of the datastructure.
+    attributes: dict[str, Any], optional
+        User-defined attributes of the datastructure.
+
+    Attributes
+    ----------
+    name: str
+        The name of the datastructure.
+    attributes : dict[str, Any]
+        User-defined attributes of the datastructure.
+    root: :class:`~compas.datastructures.TreeNode`
+        The root node of the tree.
+    nodes: set[:class:`~compas.datastructures.TreeNode`]
+        The nodes of the tree.
+    leaves: generator[:class:`~compas.datastructures.TreeNode`]
+        A generator of the leaves of the tree.
+
+    Examples
+    --------
+    >>> from compas.datastructures import Tree, TreeNode
+    >>> tree = Tree()
+    >>> root = TreeNode('root')
+    >>> branch = TreeNode('branch')
+    >>> leaf1 = TreeNode('leaf1')
+    >>> leaf2 = TreeNode('leaf2')
+    >>> tree.add_root(root)
+    >>> root.add(branch)
+    >>> branch.add(leaf1)
+    >>> branch.add(leaf2)
+    >>> print(tree)
+    <Tree with 4 nodes, 1 branches, and 2 leaves>
+    >>> tree.print()
+    <TreeNode root>
+        <TreeNode branch>
+            <TreeNode leaf2>
+            <TreeNode leaf1>
+
+    """
+
     JSONSCHEMA = {}
 
-    def __init__(self):
+    def __init__(self, name: str = None, attributes: dict = None):
         super(Tree, self).__init__()
-        self.attributes = {}
+        self.name = name
+        self.attributes = attributes or {}
         self._root = None
+        self._nodes = set()
 
     @property
     def data(self):
+        def get_node_data(node):
+            return {
+                "name": node.name,
+                "attributes": node.attributes,
+                "children": [get_node_data(child) for child in node.children],
+            }
+
         return {
-            "root": str(self.root.guid) if self.root else None,
-            "nodes": [node.data for node in self.nodes],
+            "name": self.name,
+            "root": get_node_data(self.root),
+            "attributes": self.attributes,
         }
 
+    @data.setter
+    def data(self, data):
+        self.name = data["name"]
+        self.attributes = data["attributes"]
+
+        def node_from_data(data):
+            node = TreeNode(data["name"], data["attributes"])
+            for child in data["children"]:
+                node.add(node_from_data(child))
+            return node
+
+        self.add_root(node_from_data(data["root"]))
+
     @property
     def root(self):
         return self._root
 
     def add_root(self, node: TreeNode):
-        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        """Add a root node to the tree."""
+        if not isinstance(node, TreeNode):
+            raise TypeError("The node is not a TreeNode object.")
         if not node.is_root:
             raise ValueError("The node is already part of another tree.")
         self._root = node
+        node._tree = self
+        self._nodes.add(node)
 
     def add(self, node: TreeNode, parent: TreeNode):
-        assert isinstance(node, TreeNode), "The node is not a TreeNode object."
+        """Add a node to the tree."""
+        if not isinstance(node, TreeNode):
+            raise TypeError("The node is not a TreeNode object.")
         if self.root is None:
             raise ValueError("The tree has no root node, use add_root() first.")
         else:
@@ -112,11 +221,18 @@ def add(self, node: TreeNode, parent: TreeNode):
 
     @property
     def nodes(self):
-        return list(self.root.traverse())
+        return self._nodes
+
+    def remove_root(self):
+        """Remove the root node from the tree."""
+        self._root._tree = None
+        self.nodes.remove(self._root)
+        self._root = None
 
     def remove(self, node: TreeNode):
-        if node.is_root:
-            self._root = None
+        """Remove a node from the tree."""
+        if node == self.root:
+            self.remove_root()
         else:
             node.parent.remove(node)
 
@@ -126,40 +242,18 @@ def leaves(self):
             if node.is_leaf:
                 yield node
 
-    def summary(self):
+    def __repr__(self):
         nodes = len(self.nodes)
         branches = sum(1 for node in self.nodes if node.is_branch)
         leaves = sum(1 for node in self.nodes if node.is_leaf)
-        print("Tree with {} nodes, {} branches, and {} leaves".format(nodes, branches, leaves))
+        return "<Tree with {} nodes, {} branches, and {} leaves>".format(nodes, branches, leaves)
 
     def print(self):
+        """Print the spatial hierarchy of the tree."""
+
         def _print(node, depth=0):
             print("  " * depth + str(node))
             for child in node.children:
                 _print(child, depth + 1)
 
         _print(self.root)
-
-
-if __name__ == "__main__":
-    from compas.data import json_dumps
-
-    R = TreeNode("R")
-    B = TreeNode("B")
-    L = TreeNode("L")
-    L2 = TreeNode("L2")
-
-    T = Tree()
-    T.add_root(R)
-
-    # T.add(B, R)
-    # T.add(L, B)
-    # T.add(L2, B)
-
-    R.add(B)
-    B.add(L)
-    B.add(L2)
-
-    # T.print()
-
-    print(json_dumps(T, pretty=True))

From 0b772d2bddb9cd2b5fbee959eb87b506e87bd8f9 Mon Sep 17 00:00:00 2001
From: Licini <leochen1990@gmail.com>
Date: Wed, 26 Jul 2023 15:05:03 +0200
Subject: [PATCH 04/14] adjustments based on feedback

---
 src/compas/datastructures/tree/tree.py | 37 +++++++++++++++-----------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 150da33b667..3ca2324628d 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -1,7 +1,6 @@
 from __future__ import print_function
 from __future__ import absolute_import
 from __future__ import division
-from __future__ import annotations
 
 from compas.datastructures import Datastructure
 
@@ -41,14 +40,14 @@ class TreeNode(object):
 
     """
 
-    def __init__(self, name: str = None, attributes: dict = None):
+    def __init__(self, name=None, attributes=None):
         self.name = name
         self.attributes = attributes or {}
         self._parent = None
         self._children = set()
         self._tree = None
 
-    def __repr__(self) -> str:
+    def __repr__(self):
         return "<TreeNode {}>".format(self.name)
 
     @property
@@ -75,7 +74,7 @@ def children(self):
     def tree(self):
         return self._tree
 
-    def add(self, node: TreeNode):
+    def add(self, node):
         """Add a child node to this node."""
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
@@ -85,7 +84,7 @@ def add(self, node: TreeNode):
         if self.tree:
             self.tree.nodes.add(node)
 
-    def remove(self, node: TreeNode):
+    def remove(self, node):
         """Remove a child node from this node."""
         self._children.remove(node)
         node._parent = None
@@ -94,7 +93,7 @@ def remove(self, node: TreeNode):
             self.tree.nodes.remove(node)
 
     @property
-    def acestors(self):
+    def ancestors(self):
         this = self
         while this:
             yield this
@@ -107,11 +106,20 @@ def descendants(self):
             for descendant in child.descendants:
                 yield descendant
 
-    def traverse(self):
+    def traverse(self, strategy="preorder"):
         """Traverse the tree from this node."""
-        yield self
-        for descendant in self.descendants:
-            yield descendant
+        if strategy == "preorder":
+            yield self
+            for child in self.children:
+                for node in child.traverse(strategy):
+                    yield node
+        elif strategy == "postorder":
+            for child in self.children:
+                for node in child.traverse(strategy):
+                    yield node
+            yield self
+        else:
+            raise ValueError("Unknown traversal strategy: {}".format(strategy))
 
 
 class Tree(Datastructure):
@@ -223,7 +231,7 @@ def add(self, node: TreeNode, parent: TreeNode):
     def nodes(self):
         return self._nodes
 
-    def remove_root(self):
+    def _remove_root(self):
         """Remove the root node from the tree."""
         self._root._tree = None
         self.nodes.remove(self._root)
@@ -232,7 +240,7 @@ def remove_root(self):
     def remove(self, node: TreeNode):
         """Remove a node from the tree."""
         if node == self.root:
-            self.remove_root()
+            self._remove_root()
         else:
             node.parent.remove(node)
 
@@ -243,10 +251,7 @@ def leaves(self):
                 yield node
 
     def __repr__(self):
-        nodes = len(self.nodes)
-        branches = sum(1 for node in self.nodes if node.is_branch)
-        leaves = sum(1 for node in self.nodes if node.is_leaf)
-        return "<Tree with {} nodes, {} branches, and {} leaves>".format(nodes, branches, leaves)
+        return "<Tree with {} nodes>".format(len(self.nodes))
 
     def print(self):
         """Print the spatial hierarchy of the tree."""

From 90594eb6f52d1ca46cf5bc45c86b123ba33f96e9 Mon Sep 17 00:00:00 2001
From: Licini <leochen1990@gmail.com>
Date: Wed, 26 Jul 2023 15:13:44 +0200
Subject: [PATCH 05/14] remove type hints

---
 src/compas/datastructures/tree/tree.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 3ca2324628d..d69e216c84f 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -169,7 +169,7 @@ class Tree(Datastructure):
 
     JSONSCHEMA = {}
 
-    def __init__(self, name: str = None, attributes: dict = None):
+    def __init__(self, name=None, attributes=None):
         super(Tree, self).__init__()
         self.name = name
         self.attributes = attributes or {}
@@ -208,7 +208,7 @@ def node_from_data(data):
     def root(self):
         return self._root
 
-    def add_root(self, node: TreeNode):
+    def add_root(self, node):
         """Add a root node to the tree."""
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
@@ -218,7 +218,7 @@ def add_root(self, node: TreeNode):
         node._tree = self
         self._nodes.add(node)
 
-    def add(self, node: TreeNode, parent: TreeNode):
+    def add(self, node, parent):
         """Add a node to the tree."""
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
@@ -237,7 +237,7 @@ def _remove_root(self):
         self.nodes.remove(self._root)
         self._root = None
 
-    def remove(self, node: TreeNode):
+    def remove(self, node):
         """Remove a node from the tree."""
         if node == self.root:
             self._remove_root()

From 42ca1eacba7d1d292831940e21dd33243dad0f5d Mon Sep 17 00:00:00 2001
From: Li Chen <leochen1990@gmail.com>
Date: Thu, 5 Oct 2023 14:35:58 +0200
Subject: [PATCH 06/14] docstring fixes

---
 src/compas/datastructures/tree/tree.py | 34 +++++++++++++-------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index d69e216c84f..fac4dd02b9b 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -10,32 +10,32 @@ class TreeNode(object):
 
     Parameters
     ----------
-    name: str, optional
+    name : str, optional
         The name of the tree ndoe.
-    attributes: dict[str, Any], optional
+    attributes : dict[str, Any], optional
         User-defined attributes of the datastructure.
 
     Attributes
     ----------
-    name: str
+    name : str
         The name of the datastructure.
     attributes : dict[str, Any]
         User-defined attributes of the datastructure.
-    parent: :class:`~compas.datastructures.TreeNode`
+    parent : :class:`~compas.datastructures.TreeNode`
         The parent node of the tree node.
-    children: set[:class:`~compas.datastructures.TreeNode`]
+    children : set[:class:`~compas.datastructures.TreeNode`]
         The children of the tree node.
-    tree: :class:`~compas.datastructures.Tree`
+    tree : :class:`~compas.datastructures.Tree`
         The tree the node belongs to.
-    is_root: bool
+    is_root : bool
         True if the node is the root node of the tree.
-    is_leaf: bool
+    is_leaf : bool
         True if the node is a leaf node of the tree.
-    is_branch: bool
+    is_branch : bool
         True if the node is a branch node of the tree.
-    acestors: generator[:class:`~compas.datastructures.TreeNode`]
+    acestors : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the acestors of the tree node.
-    descendants: generator[:class:`~compas.datastructures.TreeNode`]
+    descendants : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the descendants of the tree node.
 
     """
@@ -127,22 +127,22 @@ class Tree(Datastructure):
 
     Parameters
     ----------
-    name: str, optional
+    name : str, optional
         The name of the datastructure.
-    attributes: dict[str, Any], optional
+    attributes : dict[str, Any], optional
         User-defined attributes of the datastructure.
 
     Attributes
     ----------
-    name: str
+    name : str
         The name of the datastructure.
     attributes : dict[str, Any]
         User-defined attributes of the datastructure.
-    root: :class:`~compas.datastructures.TreeNode`
+    root : :class:`~compas.datastructures.TreeNode`
         The root node of the tree.
-    nodes: set[:class:`~compas.datastructures.TreeNode`]
+    nodes : set[:class:`~compas.datastructures.TreeNode`]
         The nodes of the tree.
-    leaves: generator[:class:`~compas.datastructures.TreeNode`]
+    leaves : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the leaves of the tree.
 
     Examples

From 3441105f1c15cd50fa46a36a7d3945a3816ec77a Mon Sep 17 00:00:00 2001
From: Li Chen <leochen1990@gmail.com>
Date: Thu, 5 Oct 2023 14:47:53 +0200
Subject: [PATCH 07/14] align with new data mechanism

---
 src/compas/datastructures/tree/tree.py | 42 ++++++++++++++------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index fac4dd02b9b..18c8a7fb6f1 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -74,6 +74,21 @@ def children(self):
     def tree(self):
         return self._tree
 
+    @property
+    def data(self):
+        return {
+            "name": self.name,
+            "attributes": self.attributes,
+            "children": [child.data for child in self.children],
+        }
+
+    @classmethod
+    def from_data(cls, data):
+        node = cls(data["name"], data["attributes"])
+        for child in data["children"]:
+            node.add(cls.from_data(child))
+        return node
+
     def add(self, node):
         """Add a child node to this node."""
         if not isinstance(node, TreeNode):
@@ -178,31 +193,18 @@ def __init__(self, name=None, attributes=None):
 
     @property
     def data(self):
-        def get_node_data(node):
-            return {
-                "name": node.name,
-                "attributes": node.attributes,
-                "children": [get_node_data(child) for child in node.children],
-            }
-
         return {
             "name": self.name,
-            "root": get_node_data(self.root),
+            "root": self.root.data,
             "attributes": self.attributes,
         }
 
-    @data.setter
-    def data(self, data):
-        self.name = data["name"]
-        self.attributes = data["attributes"]
-
-        def node_from_data(data):
-            node = TreeNode(data["name"], data["attributes"])
-            for child in data["children"]:
-                node.add(node_from_data(child))
-            return node
-
-        self.add_root(node_from_data(data["root"]))
+    @classmethod
+    def from_data(cls, data):
+        tree = cls(data["name"], data["attributes"])
+        root = TreeNode.from_data(data["root"])
+        tree.add_root(root)
+        return tree
 
     @property
     def root(self):

From 98dd468d6d2f51426c26be31fde7eae35e9c39c4 Mon Sep 17 00:00:00 2001
From: Li Chen <leochen1990@gmail.com>
Date: Fri, 6 Oct 2023 11:03:15 +0200
Subject: [PATCH 08/14] adjust tree functions

---
 CHANGELOG.md                           |   2 +
 src/compas/datastructures/tree/tree.py | 144 ++++++++++++++++++++-----
 2 files changed, 119 insertions(+), 27 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e94db1f1c0..172cbed3c4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Added `compas.datastructures.TreeNode` and `compas.datastructures.Tree` classes.
+
 ### Changed
 
 * Changed `Network.is_planar` to rely on `NetworkX` instead `planarity` for planarity checking.
diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 18c8a7fb6f1..5563a17bfb7 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -3,9 +3,10 @@
 from __future__ import division
 
 from compas.datastructures import Datastructure
+from compas.data import Data
 
 
-class TreeNode(object):
+class TreeNode(Data):
     """A node of a tree data structure.
 
     Parameters
@@ -90,7 +91,24 @@ def from_data(cls, data):
         return node
 
     def add(self, node):
-        """Add a child node to this node."""
+        """
+        Add a child node to this node.
+
+        Parameters
+        ----------
+        node : :class:`~compas.datastructures.TreeNode`
+            The node to add.
+
+        Returns
+        -------
+        None
+
+        Raises
+        ------
+        TypeError
+            If the node is not a :class:`~compas.datastructures.TreeNode` object.
+
+        """
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
         self._children.add(node)
@@ -100,7 +118,19 @@ def add(self, node):
             self.tree.nodes.add(node)
 
     def remove(self, node):
-        """Remove a child node from this node."""
+        """
+        Remove a child node from this node.
+
+        Parameters
+        ----------
+        node : :class:`~compas.datastructures.TreeNode`
+            The node to remove.
+
+        Returns
+        -------
+        None
+
+        """
         self._children.remove(node)
         node._parent = None
         node._tree = None
@@ -122,7 +152,26 @@ def descendants(self):
                 yield descendant
 
     def traverse(self, strategy="preorder"):
-        """Traverse the tree from this node."""
+        """
+        Traverse the tree from this node.
+
+        Parameters
+        ----------
+        strategy : str, optional
+            The traversal strategy. Options are ``"preorder"`` and ``"postorder"``.
+            Default is ``"preorder"``.
+
+        Yields
+        ------
+        :class:`~compas.datastructures.TreeNode`
+            The next node in the traversal.
+
+        Raises
+        ------
+        ValueError
+            If the strategy is not ``"preorder"`` or ``"postorder"``.
+
+        """
         if strategy == "preorder":
             yield self
             for child in self.children:
@@ -168,7 +217,7 @@ class Tree(Datastructure):
     >>> branch = TreeNode('branch')
     >>> leaf1 = TreeNode('leaf1')
     >>> leaf2 = TreeNode('leaf2')
-    >>> tree.add_root(root)
+    >>> tree.add(root)
     >>> root.add(branch)
     >>> branch.add(leaf1)
     >>> branch.add(leaf2)
@@ -210,39 +259,80 @@ def from_data(cls, data):
     def root(self):
         return self._root
 
-    def add_root(self, node):
-        """Add a root node to the tree."""
+    def add(self, node, parent=None):
+        """
+        Add a node to the tree.
+
+        Parameters
+        ----------
+        node : :class:`~compas.datastructures.TreeNode`
+            The node to add.
+        parent : :class:`~compas.datastructures.TreeNode`, optional
+            The parent node of the node to add.
+            Default is ``None``, in which case the node is added as a root node.
+
+        Returns
+        -------
+        None
+
+        Raises
+        ------
+        TypeError
+            If the node is not a :class:`~compas.datastructures.TreeNode` object.
+            If the supplied parent node is not a :class:`~compas.datastructures.TreeNode` object.
+        ValueError
+            If the node is already part of another tree.
+            If the supplied parent node is not part of this tree.
+            If the tree already has a root node, when trying to add a root node.
+
+        """
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
-        if not node.is_root:
-            raise ValueError("The node is already part of another tree.")
-        self._root = node
-        node._tree = self
-        self._nodes.add(node)
-
-    def add(self, node, parent):
-        """Add a node to the tree."""
-        if not isinstance(node, TreeNode):
-            raise TypeError("The node is not a TreeNode object.")
-        if self.root is None:
-            raise ValueError("The tree has no root node, use add_root() first.")
+
+        if node.parent:
+            raise ValueError("The node is already part of another tree, remove it from that tree first.")
+
+        if parent is None:
+            # add the node as a root node
+            if self.root is not None:
+                raise ValueError("The tree already has a root node, remove it first.")
+
+            self._root = node
+            node._tree = self
+            self._nodes.add(node)
+
         else:
+            # add the node as a child of the parent node
+            if not isinstance(parent, TreeNode):
+                raise TypeError("The parent node is not a TreeNode object.")
+
+            if parent.tree is not self:
+                raise ValueError("The parent node is not part of this tree.")
+
             parent.add(node)
 
     @property
     def nodes(self):
         return self._nodes
 
-    def _remove_root(self):
-        """Remove the root node from the tree."""
-        self._root._tree = None
-        self.nodes.remove(self._root)
-        self._root = None
-
     def remove(self, node):
-        """Remove a node from the tree."""
+        """
+        Remove a node from the tree.
+
+        Parameters
+        ----------
+        node : :class:`~compas.datastructures.TreeNode`
+            The node to remove.
+
+        Returns
+        -------
+        None
+
+        """
         if node == self.root:
-            self._remove_root()
+            self._root._tree = None
+            self.nodes.remove(self._root)
+            self._root = None
         else:
             node.parent.remove(node)
 

From 7666de49279feac5d22915136c194e46ed3feb54 Mon Sep 17 00:00:00 2001
From: Li Chen <leochen1990@gmail.com>
Date: Fri, 6 Oct 2023 11:55:39 +0200
Subject: [PATCH 09/14] simplify node tree links and add data schemas

---
 src/compas/datastructures/tree/tree.py | 53 ++++++++++++++------------
 1 file changed, 29 insertions(+), 24 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 5563a17bfb7..1c0a67abc6c 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -26,8 +26,6 @@ class TreeNode(Data):
         The parent node of the tree node.
     children : set[:class:`~compas.datastructures.TreeNode`]
         The children of the tree node.
-    tree : :class:`~compas.datastructures.Tree`
-        The tree the node belongs to.
     is_root : bool
         True if the node is the root node of the tree.
     is_leaf : bool
@@ -41,12 +39,22 @@ class TreeNode(Data):
 
     """
 
+    DATASCHEMA = {
+        "type": "object",
+        "$recursiveAnchor": True,
+        "properties": {
+            "name": {"type": "string"},
+            "attributes": {"type": "object"},
+            "children": {"type": "array", "items": {"$recursiveRef": "#"}},
+        },
+        "required": ["name", "attributes", "children"],
+    }
+
     def __init__(self, name=None, attributes=None):
-        self.name = name
+        super(TreeNode, self).__init__(name=name)
         self.attributes = attributes or {}
         self._parent = None
         self._children = set()
-        self._tree = None
 
     def __repr__(self):
         return "<TreeNode {}>".format(self.name)
@@ -71,10 +79,6 @@ def parent(self):
     def children(self):
         return self._children
 
-    @property
-    def tree(self):
-        return self._tree
-
     @property
     def data(self):
         return {
@@ -113,9 +117,6 @@ def add(self, node):
             raise TypeError("The node is not a TreeNode object.")
         self._children.add(node)
         node._parent = self
-        node._tree = self.tree
-        if self.tree:
-            self.tree.nodes.add(node)
 
     def remove(self, node):
         """
@@ -133,9 +134,6 @@ def remove(self, node):
         """
         self._children.remove(node)
         node._parent = None
-        node._tree = None
-        if self.tree:
-            self.tree.nodes.remove(node)
 
     @property
     def ancestors(self):
@@ -204,7 +202,7 @@ class Tree(Datastructure):
         User-defined attributes of the datastructure.
     root : :class:`~compas.datastructures.TreeNode`
         The root node of the tree.
-    nodes : set[:class:`~compas.datastructures.TreeNode`]
+    nodes : list[:class:`~compas.datastructures.TreeNode`]
         The nodes of the tree.
     leaves : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the leaves of the tree.
@@ -231,14 +229,21 @@ class Tree(Datastructure):
 
     """
 
-    JSONSCHEMA = {}
+    DATASCHEMA = {
+        "type": "object",
+        "properties": {
+            "name": {"type": "string"},
+            "root": TreeNode.DATASCHEMA,
+            "attributes": {"type": "object"},
+        },
+        "required": ["name", "root", "attributes"],
+    }
 
     def __init__(self, name=None, attributes=None):
         super(Tree, self).__init__()
         self.name = name
         self.attributes = attributes or {}
         self._root = None
-        self._nodes = set()
 
     @property
     def data(self):
@@ -252,7 +257,7 @@ def data(self):
     def from_data(cls, data):
         tree = cls(data["name"], data["attributes"])
         root = TreeNode.from_data(data["root"])
-        tree.add_root(root)
+        tree.add(root)
         return tree
 
     @property
@@ -298,8 +303,6 @@ def add(self, node, parent=None):
                 raise ValueError("The tree already has a root node, remove it first.")
 
             self._root = node
-            node._tree = self
-            self._nodes.add(node)
 
         else:
             # add the node as a child of the parent node
@@ -313,7 +316,11 @@ def add(self, node, parent=None):
 
     @property
     def nodes(self):
-        return self._nodes
+        if self.root:
+            for node in self.root.traverse():
+                yield node
+        else:
+            yield iter([])
 
     def remove(self, node):
         """
@@ -330,8 +337,6 @@ def remove(self, node):
 
         """
         if node == self.root:
-            self._root._tree = None
-            self.nodes.remove(self._root)
             self._root = None
         else:
             node.parent.remove(node)
@@ -343,7 +348,7 @@ def leaves(self):
                 yield node
 
     def __repr__(self):
-        return "<Tree with {} nodes>".format(len(self.nodes))
+        return "<Tree with {} nodes>".format(len(list(self.nodes)))
 
     def print(self):
         """Print the spatial hierarchy of the tree."""

From 9928394a0c802ab810820456614131f5dca53958 Mon Sep 17 00:00:00 2001
From: Li Chen <leochen1990@gmail.com>
Date: Fri, 6 Oct 2023 12:21:38 +0200
Subject: [PATCH 10/14] make tree link dynamic

---
 src/compas/datastructures/tree/tree.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 1c0a67abc6c..b99ecd47baf 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -26,6 +26,8 @@ class TreeNode(Data):
         The parent node of the tree node.
     children : set[:class:`~compas.datastructures.TreeNode`]
         The children of the tree node.
+    tree : :class:`~compas.datastructures.Tree`
+        The tree to which the node belongs.
     is_root : bool
         True if the node is the root node of the tree.
     is_leaf : bool
@@ -55,6 +57,7 @@ def __init__(self, name=None, attributes=None):
         self.attributes = attributes or {}
         self._parent = None
         self._children = set()
+        self._tree = None
 
     def __repr__(self):
         return "<TreeNode {}>".format(self.name)
@@ -79,6 +82,13 @@ def parent(self):
     def children(self):
         return self._children
 
+    @property
+    def tree(self):
+        if self.is_root:
+            return self._tree
+        else:
+            return self.parent.tree
+
     @property
     def data(self):
         return {
@@ -303,6 +313,7 @@ def add(self, node, parent=None):
                 raise ValueError("The tree already has a root node, remove it first.")
 
             self._root = node
+            node._tree = self
 
         else:
             # add the node as a child of the parent node
@@ -338,6 +349,7 @@ def remove(self, node):
         """
         if node == self.root:
             self._root = None
+            node._tree = None
         else:
             node.parent.remove(node)
 

From 7c12d19e2c140fceb15f40eab21a715886d91863 Mon Sep 17 00:00:00 2001
From: Li <leochen1990@gmail.com>
Date: Mon, 9 Oct 2023 13:02:40 +0200
Subject: [PATCH 11/14] add tests

---
 src/compas/datastructures/tree/tree.py   | 134 ++++++++++++++----
 tests/compas/datastructures/test_tree.py | 170 +++++++++++++++++++++++
 2 files changed, 278 insertions(+), 26 deletions(-)
 create mode 100644 tests/compas/datastructures/test_tree.py

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index b99ecd47baf..7aaff506f2f 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -24,7 +24,7 @@ class TreeNode(Data):
         User-defined attributes of the datastructure.
     parent : :class:`~compas.datastructures.TreeNode`
         The parent node of the tree node.
-    children : set[:class:`~compas.datastructures.TreeNode`]
+    children : list[:class:`~compas.datastructures.TreeNode`]
         The children of the tree node.
     tree : :class:`~compas.datastructures.Tree`
         The tree to which the node belongs.
@@ -37,7 +37,7 @@ class TreeNode(Data):
     acestors : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the acestors of the tree node.
     descendants : generator[:class:`~compas.datastructures.TreeNode`]
-        A generator of the descendants of the tree node.
+        A generator of the descendants of the tree node, using a depth-first preorder traversal.
 
     """
 
@@ -56,7 +56,7 @@ def __init__(self, name=None, attributes=None):
         super(TreeNode, self).__init__(name=name)
         self.attributes = attributes or {}
         self._parent = None
-        self._children = set()
+        self._children = []
         self._tree = None
 
     def __repr__(self):
@@ -125,7 +125,8 @@ def add(self, node):
         """
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
-        self._children.add(node)
+        if not node in self._children:
+            self._children.append(node)
         node._parent = self
 
     def remove(self, node):
@@ -159,14 +160,18 @@ def descendants(self):
             for descendant in child.descendants:
                 yield descendant
 
-    def traverse(self, strategy="preorder"):
+    def traverse(self, strategy="depthfirst", order="preorder"):
         """
         Traverse the tree from this node.
 
         Parameters
         ----------
-        strategy : str, optional
-            The traversal strategy. Options are ``"preorder"`` and ``"postorder"``.
+        strategy : {"depthfirst", "breadthfirst"}, optional
+            The traversal strategy.
+            Default is ``"depthfirst"``.
+
+        order : {"preorder", "postorder"}, optional
+            The traversal order. This parameter is only used for depth-first traversal.
             Default is ``"preorder"``.
 
         Yields
@@ -177,25 +182,35 @@ def traverse(self, strategy="preorder"):
         Raises
         ------
         ValueError
-            If the strategy is not ``"preorder"`` or ``"postorder"``.
+            If the strategy is not ``"depthfirst"`` or ``"breadthfirst"``.
+            If the order is not ``"preorder"`` or ``"postorder"``.
 
         """
-        if strategy == "preorder":
-            yield self
-            for child in self.children:
-                for node in child.traverse(strategy):
-                    yield node
-        elif strategy == "postorder":
-            for child in self.children:
-                for node in child.traverse(strategy):
-                    yield node
-            yield self
+        if strategy == "depthfirst":
+            if order == "preorder":
+                yield self
+                for child in self.children:
+                    for node in child.traverse(strategy, order):
+                        yield node
+            elif order == "postorder":
+                for child in self.children:
+                    for node in child.traverse(strategy, order):
+                        yield node
+                yield self
+            else:
+                raise ValueError("Unknown traversal order: {}".format(order))
+        elif strategy == "breadthfirst":
+            queue = [self]
+            while queue:
+                node = queue.pop(0)
+                yield node
+                queue.extend(node.children)
         else:
             raise ValueError("Unknown traversal strategy: {}".format(strategy))
 
 
 class Tree(Datastructure):
-    """A tree data structure.
+    """A hierarchical data structure that organizes elements into parent-child relationships. The tree starts from a unique root node, and every node (excluding the root) has exactly one parent.
 
     Parameters
     ----------
@@ -212,7 +227,7 @@ class Tree(Datastructure):
         User-defined attributes of the datastructure.
     root : :class:`~compas.datastructures.TreeNode`
         The root node of the tree.
-    nodes : list[:class:`~compas.datastructures.TreeNode`]
+    nodes : generator[:class:`~compas.datastructures.TreeNode`]
         The nodes of the tree.
     leaves : generator[:class:`~compas.datastructures.TreeNode`]
         A generator of the leaves of the tree.
@@ -250,9 +265,8 @@ class Tree(Datastructure):
     }
 
     def __init__(self, name=None, attributes=None):
-        super(Tree, self).__init__()
-        self.name = name
-        self.attributes = attributes or {}
+        super(Tree, self).__init__(name=name)
+        self.attributes.update(attributes or {})
         self._root = None
 
     @property
@@ -305,7 +319,7 @@ def add(self, node, parent=None):
             raise TypeError("The node is not a TreeNode object.")
 
         if node.parent:
-            raise ValueError("The node is already part of another tree, remove it from that tree first.")
+            raise ValueError("The node already has a parent, remove it from that parent first.")
 
         if parent is None:
             # add the node as a root node
@@ -330,8 +344,6 @@ def nodes(self):
         if self.root:
             for node in self.root.traverse():
                 yield node
-        else:
-            yield iter([])
 
     def remove(self, node):
         """
@@ -359,6 +371,76 @@ def leaves(self):
             if node.is_leaf:
                 yield node
 
+    def traverse(self, strategy="depthfirst", order="preorder"):
+        """
+        Traverse the tree from the root node.
+
+        Parameters
+        ----------
+        strategy : {"depthfirst", "breadthfirst"}, optional
+            The traversal strategy.
+            Default is ``"depthfirst"``.
+
+        order : {"preorder", "postorder"}, optional
+            The traversal order. This parameter is only used for depth-first traversal.
+            Default is ``"preorder"``.
+
+        Yields
+        ------
+        :class:`~compas.datastructures.TreeNode`
+            The next node in the traversal.
+
+        Raises
+        ------
+        ValueError
+            If the strategy is not ``"depthfirst"`` or ``"breadthfirst"``.
+            If the order is not ``"preorder"`` or ``"postorder"``.
+
+        """
+        if self.root:
+            for node in self.root.traverse(strategy=strategy, order=order):
+                yield node
+
+    def get_node_by_name(self, name):
+        """
+        Get a node by its name.
+
+        Parameters
+        ----------
+        name : str
+            The name of the node.
+
+        Returns
+        -------
+        :class:`~compas.datastructures.TreeNode`
+            The node.
+
+        """
+        for node in self.nodes:
+            if node.name == name:
+                return node
+
+    def get_nodes_by_name(self, name):
+        """
+        Get all nodes by their name.
+
+        Parameters
+        ----------
+        name : str
+            The name of the node.
+
+        Returns
+        -------
+        list[:class:`~compas.datastructures.TreeNode`]
+            The nodes.
+
+        """
+        nodes = []
+        for node in self.nodes:
+            if node.name == name:
+                nodes.append(node)
+        return nodes
+
     def __repr__(self):
         return "<Tree with {} nodes>".format(len(list(self.nodes)))
 
diff --git a/tests/compas/datastructures/test_tree.py b/tests/compas/datastructures/test_tree.py
new file mode 100644
index 00000000000..b7709d23bf4
--- /dev/null
+++ b/tests/compas/datastructures/test_tree.py
@@ -0,0 +1,170 @@
+import pytest
+
+from compas.datastructures import Tree, TreeNode
+from compas.data import json_dumps, json_loads
+import json
+
+# =============================================================================
+# Fixtures
+# =============================================================================
+
+
+@pytest.fixture
+def simple_tree():
+    # A basic fixture for a simple tree
+    root = TreeNode(name="root")
+    branch1 = TreeNode(name="branch1")
+    branch2 = TreeNode(name="branch2")
+    leaf1_1 = TreeNode(name="leaf1_1")
+    leaf1_2 = TreeNode(name="leaf1_2")
+    leaf2_1 = TreeNode(name="leaf2_1")
+    leaf2_2 = TreeNode(name="leaf2_2")
+
+    tree = Tree()
+    tree.add(root)
+    tree.add(branch1, parent=root)
+    tree.add(branch2, parent=root)
+    tree.add(leaf1_1, parent=branch1)
+    tree.add(leaf1_2, parent=branch1)
+    tree.add(leaf2_1, parent=branch2)
+    tree.add(leaf2_2, parent=branch2)
+    return tree
+
+
+# =============================================================================
+# Basics
+# =============================================================================
+
+
+def test_treenode_initialization():
+    node = TreeNode(name="test")
+    assert node.name == "test"
+    assert node.parent is None
+    assert node.tree is None
+    assert len(node.children) == 0
+
+
+def test_tree_initialization():
+    tree = Tree(name="test")
+    assert tree.name == "test"
+    assert tree.root is None
+
+
+# =============================================================================
+# TreeNode Properties
+# =============================================================================
+
+
+def test_treenode_properties(simple_tree):
+    root = simple_tree.root
+    branch1, branch2 = list(root.children)
+    leaf1_1, leaf1_2 = list(branch1.children)
+    leaf2_1, leaf2_2 = list(branch2.children)
+
+    assert root.is_root == True
+    assert root.is_leaf == False
+    assert root.is_branch == False
+
+    assert branch1.is_root == False
+    assert branch1.is_leaf == False
+    assert branch1.is_branch == True
+
+    assert branch2.is_root == False
+    assert branch2.is_leaf == False
+    assert branch2.is_branch == True
+
+    assert leaf1_1.is_root == False
+    assert leaf1_1.is_leaf == True
+    assert leaf1_1.is_branch == False
+
+    assert leaf1_2.is_root == False
+    assert leaf1_2.is_leaf == True
+    assert leaf1_2.is_branch == False
+
+    assert leaf2_1.is_root == False
+    assert leaf2_1.is_leaf == True
+    assert leaf2_1.is_branch == False
+
+    assert leaf2_2.is_root == False
+    assert leaf2_2.is_leaf == True
+    assert leaf2_2.is_branch == False
+
+
+# =============================================================================
+# Tree Properties
+# =============================================================================
+
+
+def test_tree_properties(simple_tree):
+    nodes = list(simple_tree.nodes)
+    leaves = list(simple_tree.leaves)
+
+    assert len(nodes) == 7
+    assert len(leaves) == 4
+
+
+# =============================================================================
+# Tree Traversal
+# =============================================================================
+
+
+def test_tree_traversal(simple_tree):
+    nodes = [node.name for node in simple_tree.traverse(strategy="depthfirst", order="preorder")]
+    assert nodes == ["root", "branch1", "leaf1_1", "leaf1_2", "branch2", "leaf2_1", "leaf2_2"]
+
+    nodes = [node.name for node in simple_tree.traverse(strategy="depthfirst", order="postorder")]
+    assert nodes == ["leaf1_1", "leaf1_2", "branch1", "leaf2_1", "leaf2_2", "branch2", "root"]
+
+    nodes = [node.name for node in simple_tree.traverse(strategy="breadthfirst")]
+    assert nodes == ["root", "branch1", "branch2", "leaf1_1", "leaf1_2", "leaf2_1", "leaf2_2"]
+
+
+# =============================================================================
+# Tree Manipulation
+# =============================================================================
+
+
+def test_tree_add_node(simple_tree):
+    branch2 = simple_tree.get_node_by_name("branch2")
+    branch2.add(TreeNode(name="test"))
+
+    assert len(list(branch2.children)) == 3
+    assert len(list(simple_tree.nodes)) == 8
+
+
+def test_tree_remove_node(simple_tree):
+    branch2 = simple_tree.get_node_by_name("branch2")
+    leaf2_1 = simple_tree.get_node_by_name("leaf2_1")
+    branch2.remove(leaf2_1)
+
+    assert len(list(branch2.children)) == 1
+    assert len(list(simple_tree.nodes)) == 6
+
+    root = simple_tree.root
+    branch1 = simple_tree.get_node_by_name("branch1")
+    root.remove(branch1)
+
+    assert len(list(root.children)) == 1
+    assert len(list(simple_tree.nodes)) == 3
+
+
+# =============================================================================
+# Tree Serialization
+# =============================================================================
+
+
+def test_tree_serialization(simple_tree):
+    serialized = json_dumps(simple_tree)
+    deserialized = json_loads(serialized)
+    assert simple_tree.data == deserialized.data
+
+    test_tree_properties(deserialized)
+    test_tree_traversal(deserialized)
+    test_tree_add_node(deserialized)
+    test_tree_remove_node(json_loads(serialized))
+
+
+def test_data_validation(simple_tree):
+    serialized = json_dumps(simple_tree)
+    data = json.loads(serialized)["data"]
+    assert Tree.validate_data(data)

From a0d2b4f56f067378b7257342579ede4981b3c2de Mon Sep 17 00:00:00 2001
From: Li <leochen1990@gmail.com>
Date: Mon, 9 Oct 2023 13:06:49 +0200
Subject: [PATCH 12/14] lint

---
 src/compas/datastructures/tree/tree.py   |  2 +-
 tests/compas/datastructures/test_tree.py | 42 ++++++++++++------------
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 7aaff506f2f..cb11a863d2e 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -125,7 +125,7 @@ def add(self, node):
         """
         if not isinstance(node, TreeNode):
             raise TypeError("The node is not a TreeNode object.")
-        if not node in self._children:
+        if node not in self._children:
             self._children.append(node)
         node._parent = self
 
diff --git a/tests/compas/datastructures/test_tree.py b/tests/compas/datastructures/test_tree.py
index b7709d23bf4..29fb8c2910e 100644
--- a/tests/compas/datastructures/test_tree.py
+++ b/tests/compas/datastructures/test_tree.py
@@ -61,33 +61,33 @@ def test_treenode_properties(simple_tree):
     leaf1_1, leaf1_2 = list(branch1.children)
     leaf2_1, leaf2_2 = list(branch2.children)
 
-    assert root.is_root == True
-    assert root.is_leaf == False
-    assert root.is_branch == False
+    assert root.is_root is True
+    assert root.is_leaf is False
+    assert root.is_branch is False
 
-    assert branch1.is_root == False
-    assert branch1.is_leaf == False
-    assert branch1.is_branch == True
+    assert branch1.is_root is False
+    assert branch1.is_leaf is False
+    assert branch1.is_branch is True
 
-    assert branch2.is_root == False
-    assert branch2.is_leaf == False
-    assert branch2.is_branch == True
+    assert branch2.is_root is False
+    assert branch2.is_leaf is False
+    assert branch2.is_branch is True
 
-    assert leaf1_1.is_root == False
-    assert leaf1_1.is_leaf == True
-    assert leaf1_1.is_branch == False
+    assert leaf1_1.is_root is False
+    assert leaf1_1.is_leaf is True
+    assert leaf1_1.is_branch is False
 
-    assert leaf1_2.is_root == False
-    assert leaf1_2.is_leaf == True
-    assert leaf1_2.is_branch == False
+    assert leaf1_2.is_root is False
+    assert leaf1_2.is_leaf is True
+    assert leaf1_2.is_branch is False
 
-    assert leaf2_1.is_root == False
-    assert leaf2_1.is_leaf == True
-    assert leaf2_1.is_branch == False
+    assert leaf2_1.is_root is False
+    assert leaf2_1.is_leaf is True
+    assert leaf2_1.is_branch is False
 
-    assert leaf2_2.is_root == False
-    assert leaf2_2.is_leaf == True
-    assert leaf2_2.is_branch == False
+    assert leaf2_2.is_root is False
+    assert leaf2_2.is_leaf is True
+    assert leaf2_2.is_branch is False
 
 
 # =============================================================================

From c0ba4de4e8d41de724f6a15db8056761081a6273 Mon Sep 17 00:00:00 2001
From: Li <leochen1990@gmail.com>
Date: Mon, 9 Oct 2023 13:32:30 +0200
Subject: [PATCH 13/14] skip data validate for ipy

---
 src/compas/datastructures/tree/tree.py   |  4 ----
 tests/compas/datastructures/test_tree.py | 11 +++++------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index cb11a863d2e..9d78ae05a1f 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -168,11 +168,9 @@ def traverse(self, strategy="depthfirst", order="preorder"):
         ----------
         strategy : {"depthfirst", "breadthfirst"}, optional
             The traversal strategy.
-            Default is ``"depthfirst"``.
 
         order : {"preorder", "postorder"}, optional
             The traversal order. This parameter is only used for depth-first traversal.
-            Default is ``"preorder"``.
 
         Yields
         ------
@@ -379,11 +377,9 @@ def traverse(self, strategy="depthfirst", order="preorder"):
         ----------
         strategy : {"depthfirst", "breadthfirst"}, optional
             The traversal strategy.
-            Default is ``"depthfirst"``.
 
         order : {"preorder", "postorder"}, optional
             The traversal order. This parameter is only used for depth-first traversal.
-            Default is ``"preorder"``.
 
         Yields
         ------
diff --git a/tests/compas/datastructures/test_tree.py b/tests/compas/datastructures/test_tree.py
index 29fb8c2910e..384a9091f12 100644
--- a/tests/compas/datastructures/test_tree.py
+++ b/tests/compas/datastructures/test_tree.py
@@ -1,8 +1,9 @@
 import pytest
+import compas
+import json
 
 from compas.datastructures import Tree, TreeNode
 from compas.data import json_dumps, json_loads
-import json
 
 # =============================================================================
 # Fixtures
@@ -163,8 +164,6 @@ def test_tree_serialization(simple_tree):
     test_tree_add_node(deserialized)
     test_tree_remove_node(json_loads(serialized))
 
-
-def test_data_validation(simple_tree):
-    serialized = json_dumps(simple_tree)
-    data = json.loads(serialized)["data"]
-    assert Tree.validate_data(data)
+    if not compas.IPY:
+        data = json.loads(serialized)["data"]
+        assert Tree.validate_data(data)

From f3ef02bb12e3652a0d9bd519ea0013b93c964c19 Mon Sep 17 00:00:00 2001
From: Li <leochen1990@gmail.com>
Date: Mon, 9 Oct 2023 15:29:42 +0200
Subject: [PATCH 14/14] no spaces

---
 src/compas/datastructures/tree/tree.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/compas/datastructures/tree/tree.py b/src/compas/datastructures/tree/tree.py
index 9d78ae05a1f..7d55c7fcb94 100644
--- a/src/compas/datastructures/tree/tree.py
+++ b/src/compas/datastructures/tree/tree.py
@@ -168,7 +168,6 @@ def traverse(self, strategy="depthfirst", order="preorder"):
         ----------
         strategy : {"depthfirst", "breadthfirst"}, optional
             The traversal strategy.
-
         order : {"preorder", "postorder"}, optional
             The traversal order. This parameter is only used for depth-first traversal.
 
@@ -377,7 +376,6 @@ def traverse(self, strategy="depthfirst", order="preorder"):
         ----------
         strategy : {"depthfirst", "breadthfirst"}, optional
             The traversal strategy.
-
         order : {"preorder", "postorder"}, optional
             The traversal order. This parameter is only used for depth-first traversal.