update stack and queue.

codes/python/chapter_stack_and_queue/array_stack.py

@@ -59,6 +59,10 @@ if __name__ == "__main__":
     peek = stack.peek()
     print("栈顶元素 peek =", peek)
 
+    """ 访问索引 index 处元素 """
+    num = stack.get(3);
+    print("栈索引 3 处的元素为 num =", num);
+
     """ 元素出栈 """
     pop = stack.pop()
     print("出栈元素 pop =", pop)

codes/python/chapter_stack_and_queue/linkedlist_stack.py

@@ -31,12 +31,10 @@ class LinkedListStack:
 
     """ 出栈 """
     def pop(self):
-        # 判空处理
-        if not self.__peek: return None
-        pop = self.__peek.val
+        num = self.peek()
         self.__peek = self.__peek.next
         self.__size -= 1
-        return pop
+        return num
 
     """ 访问栈顶元素 """
     def peek(self):