Add leaves property (#177)

* test

* implementation of leaves

* add leaves to public API

* whatsnew

Author: TomNicholas

datatree/tests/test_treenode.py

@@ -326,6 +326,18 @@ def test_descendants(self):
         for node, expected_name in zip(descendants, expected):
             assert node.name == expected_name
 
+    def test_leaves(self):
+        tree, _ = create_test_tree()
+        leaves = tree.leaves
+        expected = [
+            "d",
+            "f",
+            "g",
+            "i",
+        ]
+        for node, expected_name in zip(leaves, expected):
+            assert node.name == expected_name
+
 
 class TestRenderTree:
     def test_render_nodetree(self):

datatree/treenode.py

@@ -267,14 +267,27 @@ def root(self: Tree) -> Tree:
 
     @property
     def is_root(self) -> bool:
-        """Whether or not this node is the tree root."""
+        """Whether this node is the tree root."""
         return self.parent is None
 
     @property
     def is_leaf(self) -> bool:
-        """Whether or not this node is a leaf node."""
+        """
+        Whether this node is a leaf node.
+
+        Leaf nodes are defined as nodes which have no children.
+        """
         return self.children == {}
 
+    @property
+    def leaves(self: Tree) -> Tuple[Tree, ...]:
+        """
+        All leaf nodes.
+
+        Leaf nodes are defined as nodes which have no children.
+        """
+        return tuple([node for node in self.subtree if node.is_leaf])
+
     @property
     def siblings(self: Tree) -> OrderedDict[str, Tree]:
         """
@@ -307,7 +320,7 @@ def subtree(self: Tree) -> Iterator[Tree]:
         return iterators.PreOrderIter(self)
 
     @property
-    def descendants(self: Tree) -> Tuple[Tree]:
+    def descendants(self: Tree) -> Tuple[Tree, ...]:
         """
         Child nodes and all their child nodes.
 
@@ -319,7 +332,7 @@ def descendants(self: Tree) -> Tuple[Tree]:
         """
         all_nodes = tuple(self.subtree)
         this_node, *descendants = all_nodes
-        return tuple(descendants)  # type: ignore[return-value]
+        return tuple(descendants)
 
     def _pre_detach(self: Tree, parent: Tree) -> None:
         """Method call before detaching from `parent`."""
@@ -563,7 +576,7 @@ def find_common_ancestor(self, other: NamedNode) -> NamedNode:
 
         if not common_ancestor:
             raise NotFoundInTreeError(
-                "Cannot find relative path because nodes do not lie within the same tree"
+                "Cannot find common ancestor because nodes do not lie within the same tree"
             )
 
         return common_ancestor

docs/source/api.rst

@@ -30,6 +30,7 @@ Attributes relating to the recursive tree-like structure of a ``DataTree``.
    DataTree.root
    DataTree.is_root
    DataTree.is_leaf
+   DataTree.leaves
    DataTree.subtree
    DataTree.descendants
    DataTree.siblings

docs/source/whats-new.rst

@@ -29,6 +29,8 @@ New Features
   By `Tom Nicholas <https://github.com/TomNicholas>`_.
 - Added a new :py:meth:`DataTree.descendants` property (:pull:`170`).
   By `Tom Nicholas <https://github.com/TomNicholas>`_.
+- Added a :py:meth:`DataTree.leaves` property (:pull:`177`).
+  By `Tom Nicholas <https://github.com/TomNicholas>`_.
 
 Breaking changes
 ~~~~~~~~~~~~~~~~