Question

我正在尝试构建一个二叉搜索树库，我的代码片段出现语法错误：

class Node:
    """
    Tree node: Left and Right child + data which can be any object
    """
    def __init__(self,data):
        """
        Node constructor
        """
        self.left = None
        self.right = None
        self.data = data

def insert(self,data):                     # self --> object self.data
    """
    Insert new node with data
    """
    if data < self.data:                   # insert data less than current root 
        if self.left is None:              # if left node is empty, 
            self.left = Node(data)         # object left --> Node with new data
        else:
            self.left.insert(data)         # if left node is not empty, go insert again
    else:
        if self.right is None:             # insert data greater than current node
            self.right = Node(data)        # object right --> Node with new data
        else:
            self.right.insert(data)        # if not empty, run insert again


def lookup(self, data, parent = None):
    """
    Lookup node containing data
    """
    if data < self.data:
        if self.left is None:
            return None, None
        return self.left.lookup(data,self)   
    elif data > self.data:
        if self.right is None:
            return None, None
        return self.right.lookup(data,self)
    else:
        return self, parent

def delete(self, data):
    """
    delete node containing data
    """

    """ no child """
    if children_count == 0:
        # if node has no children, remove it
        if parent.left is node:        # if parent is pointing to current node
            parent.left = None         # set parent pointing left to None
        else:
            parent.right = None        # else set parent pointing right to None
        del node                       # del node

    """ 1 child """    
    elif children_count == 1:
        # if node has 1 child
        # replace node by it's child
        if node.left:
            n = node.left
        else:
            n = node.right
        if parent:
            if parent.left is node:
                parent.left = n
            else:
                parent.right = n
        del node

    """ 2 children """
    else:
        # if node has 2 children
        # find its successor 
        parent = node                                        # parent is equal to current node target of deletion
        successor = node.right                               # successor is right of the node
        while successor.left:                                 
            parent = successor                               
            successor = successor.left
        # replace node data by its successor data
        node.data = successor.data
        #fix successor's parent's child
        if parent.left == successor:
            parent.left = successor.right
        else:
            parent.right = successor.right


def children_count(self):
    """ Return the number of children """
    if node is None:
        return None
    cnt = 0
    if self.left:
        cnt += 1
    if self.right:
        cnt += 1
    return cnt


# method to print tree in order. Use recursion inside print_tree() to walk the tree breath-first 

def print_tree(self):
    if self.left:
        self.left.print_tree()
    print self.data,
    if self.right:
        self.right.print_tree()

错误是：

Traceback (most recent call last):
  File "<pyshell#10>", line 1, in <module>
    import BSTlib
  File "BSTlib.py", line 78
    elif children_count == 1:
       ^

我似乎无法看出有什么问题= [有人可以帮我指出这一点吗？谢谢！

Answer 1

这是docstring和whitespace的错误。运行以下代码：

if False:
    print 'hi'

"""1 child"""
elif True:
    print 'sdf'

你得到一个类似的SyntaxError。

删除docstring（或只是移动它）并删除额外的空格：

if False:
    print 'hi'
elif True:
    print 'sdf'

如果您需要发表评论，那么只需使用哈希#：

if False:
    print 'hi'
# 1 child
elif True:
    print 'sdf'

看不到语法错误

1 个答案: