GH-144: add python tree

README.md

@@ -90,6 +90,7 @@ A data structure is a data organization, management, and storage format that is
 <td>Tree</td>
 <td>
 <a href="/concepts/cpp/tree.md"><code>cpp🐀</code></a>
+<a href="/concepts/python/tree.md"><code>py🐍</code></a>
 </td>
 </tr>
 <tr>

concepts/python/tree.md

@@ -0,0 +1,76 @@
+# Tree
+
+From wikipedia
+
+> In computer science, a tree is a widely used abstract data type that represents a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be connected to exactly one parent, except for the root node, which has no parent.
+
+![](../abstract/data-structures/tree.png)
+
+
+## 🎨 Tree Design
+
+**Properties**
+
+|          | Definition       |
+| -------- | ---------------- |
+| value    | value of node    |
+| parent   | parent of node   |
+| children | children of node |
+
+**Methods**
+
+|           | Definition                  |
+| --------- | --------------------------- |
+| Node()    | Construct node from a value |
+| set_child | set child to the node       |
+
+
+## 📈 Complexity Analysis of Tree
+
+| Operation | Complexity |
+| --------- | ---------- |
+| set_child | $O(1)$     |
+
+## 💻 Tree Implementation in Python
+
+Here are the implementation of Tree in Python from scratch.
+
+```python
+import random
+import string
+
+
+class Node(object):
+    def __init__(self, value, children=None, parent=None):
+        self.value = value
+        self.parent = parent
+        if parent is not None:
+            parent.add_child(self)
+        self.children = []
+        if children is not None:
+            for child in children:
+                self.add_child(child)
+
+    def __repr__(self):
+        return str(self.value)
+
+    def add_child(self, node):
+        node.parent = self
+        assert isinstance(node, Node)
+        self.children.append(node)
+
+if __name__ == '__main__':
+    root_node = Node(value=1)
+    child_node_1 = Node(value=2, parent=root_node)
+    child_node_2 = Node(value=3, parent=root_node)
+    print(root_node)               # 1
+    print(root_node.children)      # [2, 3]
+    print(child_node_1.parent)     # 1
+```
+
+
+## 🔗 Further Reading
+
+* [Tree (data structures)](https://en.wikipedia.org/wiki/Tree_(data_structure)), wikipedia
+* [Python Tree Implementation with BigTree](https://towardsdatascience.com/python-tree-implementation-with-bigtree-13cdabd77adc), towardsdatascience 2022
+* ▶️ [Data Structures: Trees](https://www.youtube.com/watch?v=oSWTXtMglKE), HackerRank