Pyupgrade to Python 3.9 (#4718)

* Pyupgrade to Python 3.9

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

data_structures/linked_list/merge_two_lists.py

@@ -5,7 +5,6 @@ from __future__ import annotations
 
 from collections.abc import Iterable, Iterator
 from dataclasses import dataclass
-from typing import Optional
 
 test_data_odd = (3, 9, -11, 0, 7, 5, 1, -1)
 test_data_even = (4, 6, 2, 0, 8, 10, 3, -2)
@@ -14,12 +13,12 @@ test_data_even = (4, 6, 2, 0, 8, 10, 3, -2)
 @dataclass
 class Node:
     data: int
-    next: Optional[Node]
+    next: Node | None
 
 
 class SortedLinkedList:
     def __init__(self, ints: Iterable[int]) -> None:
-        self.head: Optional[Node] = None
+        self.head: Node | None = None
         for i in reversed(sorted(ints)):
             self.head = Node(i, self.head)
 

data_structures/linked_list/print_reverse.py

@@ -1,4 +1,4 @@
-from typing import List
+from __future__ import annotations
 
 
 class Node:
@@ -16,7 +16,7 @@ class Node:
         return "->".join(string_rep)
 
 
-def make_linked_list(elements_list: List):
+def make_linked_list(elements_list: list):
     """Creates a Linked List from the elements of the given sequence
     (list/tuple) and returns the head of the Linked List.
     >>> make_linked_list([])

data_structures/linked_list/skip_list.py

@@ -2,11 +2,10 @@
 Based on "Skip Lists: A Probabilistic Alternative to Balanced Trees" by William Pugh
 https://epaperpress.com/sortsearch/download/skiplist.pdf
 """
-
 from __future__ import annotations
 
 from random import random
-from typing import Generic, Optional, TypeVar
+from typing import Generic, TypeVar
 
 KT = TypeVar("KT")
 VT = TypeVar("VT")
@@ -124,7 +123,7 @@ class SkipList(Generic[KT, VT]):
 
         return level
 
-    def _locate_node(self, key) -> tuple[Optional[Node[KT, VT]], list[Node[KT, VT]]]:
+    def _locate_node(self, key) -> tuple[Node[KT, VT] | None, list[Node[KT, VT]]]:
         """
         :param key: Searched key,
         :return: Tuple with searched node (or None if given key is not present)
@@ -222,7 +221,7 @@ class SkipList(Generic[KT, VT]):
                 else:
                     update_node.forward[i] = new_node
 
-    def find(self, key: VT) -> Optional[VT]:
+    def find(self, key: VT) -> VT | None:
         """
         :param key: Search key.
         :return: Value associated with given key or None if given key is not present.