initial add for the plugin

remove fstring

migrate to Tree classmethod

tests/test_tree.py

@@ -35,6 +35,14 @@ def setUp(self):
         #       |-- George
         self.tree = tree
         self.copytree = Tree(self.tree, deep=True)
+        self.input_dict = {
+            "Bill": "Harry",
+            "Jane": "Harry",
+            "Harry": None,
+            "Diane": "Jane",
+            "Mark": "Jane",
+            "Mary": "Harry",
+        }
 
     @staticmethod
     def get_t1():
@@ -734,3 +742,29 @@ def test_root_removal(self):
         t.create_node(identifier="root-B")
         self.assertEqual(len(t.nodes.keys()), 1)
         self.assertEqual(t.root, "root-B")
+
+    def test_from_map(self):
+        tree = Tree.from_map(self.input_dict)
+        self.assertTrue(tree.size() == 6)
+        self.assertTrue(
+            tree.root == [k for k, v in self.input_dict.items() if v is None][0]
+        )
+        tree = Tree.from_map(self.input_dict, id_func=lambda x: x.upper())
+        self.assertTrue(tree.size() == 6)
+
+        def data_func(x):
+            return x.upper()
+
+        tree = Tree.from_map(self.input_dict, data_func=data_func)
+        self.assertTrue(tree.size() == 6)
+        self.assertTrue(
+            tree.get_node(tree.root).data
+            == data_func([k for k, v in self.input_dict.items() if v is None][0])
+        )
+        with self.assertRaises(ValueError):
+            # invalid input payload without a root
+            tree = Tree.from_map({"a": "b"})
+
+        with self.assertRaises(ValueError):
+            # invalid input payload without more than 1 root
+            tree = Tree.from_map({"a": None, "b": None})

treelib/tree.py

@@ -1128,3 +1128,37 @@ def to_graphviz(
             print(f.getvalue())
 
         f.close()
+
+    @classmethod
+    def from_map(cls, child_parent_dict, id_func=None, data_func=None):
+        '''
+        takes a dict with child:parent, and form a tree
+        '''
+        tree = Tree()
+        if tree is None or tree.size() > 0:
+            raise ValueError('need to pass in an empty tree')
+        id_func = id_func if id_func else lambda x: x
+        data_func = data_func if data_func else lambda x: None
+        parent_child_dict = {}
+        root_node = None
+        for k, v in child_parent_dict.items():
+            if v is None and root_node is None:
+                root_node = k
+            elif v is None and root_node is not None:
+                raise ValueError('invalid input, more than 1 child has no parent')
+            else:
+                if v in parent_child_dict:
+                    parent_child_dict[v].append(k)
+                else:
+                    parent_child_dict[v] = [k]
+        if root_node is None:
+            raise ValueError('cannot find root')
+
+        tree.create_node(root_node, id_func(root_node), data=data_func(root_node))
+        queue = [root_node]
+        while len(queue) > 0:
+            parent_node = queue.pop()
+            for child in parent_child_dict.get(parent_node, []):
+                tree.create_node(child, id_func(child), parent=id_func(parent_node), data=data_func(child))
+                queue.append(child)
+        return tree