Add typing annotations to Python codes. (#411)

codes/python/modules/linked_list.py

@@ -4,22 +4,16 @@ Created Time: 2021-12-11
 Author: Krahets (krahets@163.com)
 """
 
+from typing import List, Optional
+
 class ListNode:
-    """Definition for a singly-linked list node
-    """    
-    def __init__(self, val=0, next=None):
-        self.val = val
-        self.next = next
+    """ Definition for a singly-linked list node """
+    def __init__(self, val: int):
+        self.val: int = val                  # 结点值
+        self.next: Optional[ListNode] = None # 后继结点引用
 
-def list_to_linked_list(arr):
-    """Generate a linked list with a list
-
-    Args:
-        arr ([type]): [description]
-
-    Returns:
-        [type]: [description]
-    """    
+def list_to_linked_list(arr: List[int]) -> Optional[ListNode]:
+    """ Generate a linked list with a list """
     dum = head = ListNode(0)
     for a in arr:
         node = ListNode(a)
@@ -27,31 +21,16 @@ def list_to_linked_list(arr):
         head = head.next
     return dum.next
 
-def linked_list_to_list(head):
-    """Serialize a linked list into an array
-
-    Args:
-        head ([type]): [description]
-
-    Returns:
-        [type]: [description]
-    """    
-    arr = []
+def linked_list_to_list(head: Optional[ListNode]) -> List[int]:
+    """ Serialize a linked list into an array """
+    arr: List[int] = []
     while head:
         arr.append(head.val)
         head = head.next
     return arr
 
-def get_list_node(head, val):
-    """Get a list node with specific value from a linked list
-
-    Args:
-        head ([type]): [description]
-        val ([type]): [description]
-
-    Returns:
-        [type]: [description]
-    """    
+def get_list_node(head: Optional[ListNode], val: int) -> Optional[ListNode]:
+    """ Get a list node with specific value from a linked list """
     while head and head.val != val:
         head = head.next
     return head