在VSCode平台上全代码： class TreeNode:     def __init__(self, x):         self.val = x         self.left = None         self.right = None class Solution:         def Serialize(self, root):         # write code here         if not root:             return ""         self.number = []         self.cur = []         self.number.append(root)         self.Se(root)         #print(self.cur)         return ",".join(self.cur)     def Se(self,root):         while(self.number):             if self.number[0] != "#" and self.number[0]:                 self.cur.append(str(self.number[0].val))#AttributeError: 'NoneType' object has no attribute 'val',number[0]==None                 if self.number[0].left:                     self.number.append(self.number[0].left)                 if self.number[0].right:                     self.number.append(self.number[0].right)#没有判断语句，一直循环，self.number[None]                 self.number.pop(0)             if len(self.number)>0 and self.number[0]=="#":                 self.cur.append("#")#IndexError: list index out of range                 self.number.pop(0)             #if not self.number[0]:     def Deserialize(self, s):         # write code here         if not s:             return         l = s.split(",")         root = TreeNode(None)         return(self.listCreatTree(root,l,0))     def listCreatTree(self, root,l,i):         if i < len(l):             val = l[i]             if val != "#":                 root = TreeNode(val)                 root.left = self.listCreatTree(root, l, 2*i+1)                 root.right = self.listCreatTree(root, l, 2*i+2)                 return root             if val == "#":                 root = TreeNode(val)                 return root         '''     flag=-1     def Serialize(self, root):         # write code here         if not root:             return '#'         return str(root.val)+','+self.Serialize(root.left)+','+self.Serialize(root.right)             def Deserialize(self, s):         # write code here         #print(s)         self.flag+=1         lis=s.split(',')                 if self.flag>=len(lis):             return None                 root=None         #print("----------",self.flag,len(lis),len(s))         if lis[self.flag]!='#':             root=TreeNode(int(lis[self.flag]))             root.left=self.Deserialize(s)             root.right=self.Deserialize(s)         return root     '''     def midTraversal(self, root):         if root:             self.midTraversal(root.left)             print(root.val)             self.midTraversal(root.right) if __name__ == "__main__":     #b = [8,6,10,5,7,9,11]     #print()     #print(list(b))     #print(b.split(","))     a = Solution()     root = TreeNode(None)     root = a.Deserialize("8,6,10,5,7,9,11")     print("+++++")     a.midTraversal(root)     print("--------------------")     print(a.Serialize(root))