delitem method (#88)

* test

* method

* whatsnew

Author: TomNicholas

datatree/tests/test_treenode.py

@@ -227,9 +227,18 @@ def test_overwrite_child(self):
         assert marys_evil_twin.parent is john
 
 
-# TODO write and test all the del methods
 class TestPruning:
-    ...
+    def test_del_child(self):
+        john = TreeNode()
+        mary = TreeNode()
+        john._set_item("Mary", mary)
+
+        del john["Mary"]
+        assert "Mary" not in john.children
+        assert mary.parent is None
+
+        with pytest.raises(KeyError):
+            del john["Mary"]
 
 
 def create_test_tree():

datatree/treenode.py

@@ -438,8 +438,14 @@ def _set_item(
         else:
             current_node._set(name, item)
 
-    def del_node(self, path: str):
-        raise NotImplementedError
+    def __delitem__(self: Tree, key: str):
+        """Remove a child node from this tree object."""
+        if key in self.children:
+            child = self._children[key]
+            del self._children[key]
+            child.orphan()
+        else:
+            raise KeyError("Cannot delete")
 
     def update(self: Tree, other: Mapping[str, Tree]) -> None:
         """

docs/source/whats-new.rst

@@ -36,6 +36,8 @@ New Features
   By `Tom Nicholas <https://github.com/TomNicholas>`_.
 - New HTML repr, which will automatically display in a jupyter notebook. (:pull:`78`)
   By `Tom Nicholas <https://github.com/TomNicholas>`_.
+- New delitem method so you can delete nodes. (:pull:`88`)
+  By `Tom Nicholas <https://github.com/TomNicholas>`_.
 
 Breaking changes
 ~~~~~~~~~~~~~~~~