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在python中遍历树层次结构？

python recursion tree

在python中遍历树层次结构？,python,recursion,tree,Python,Recursion,Tree,我是新来的，对python很陌生 我们有一个家庭作业，我已经可以做剩下的了，但还有一个问题： 如果我有这样的树层次结构： root = [ parent1 = [ child1, child2 = [ sub_child ] child3 ], parent2 = [ child1, child2 ] ] 它们都是一个名为TreeHierarc

我是新来的，对python很陌生

我们有一个家庭作业，我已经可以做剩下的了，但还有一个问题： 如果我有这样的树层次结构：

root = [
    parent1 = [
        child1,
        child2 = [
            sub_child
        ]
        child3
    ],
    parent2 = [
        child1,
        child2
    ]
]
它们都是一个名为
TreeHierarchyClass
的类的实例，它们都有一个name属性，我怎么才能找到我输入了name的类呢

我尝试使用for循环，但无法知道我需要多少？获取名称很容易：

name = input("Enter name: ")
if name == TreeHierarchyObject.name:
    print("Found it!")
但是如何循环对象呢？

这里应该使用简单的递归。 该方法稍微取决于子对象附着到父对象的方式

如果他们在一个列表中，我建议这样做，那么这一个就可以了。 只需在类中定义以下方法：

def findObjectByName(self, name):
    if self.name == name:
        return self
    else:
        for child in self.children:
            match = child.findObjectByName(name)
            if match:
                return match
编辑： 要使此操作适用于任何属性，而不仅仅是名称，请改用
getattr（）
：

def findObject(self, attr, value):
    if getattr(self, attr) == value:
        return self
    else:
        for child in self.children:
            match = child.findObject(attr, value)
            if match:
                return match
只需调用
root.findObject（“Sub-Child！”）
或使用第二种方法：
root.findObject（“name”，“Sub-Child！”）
您应该在这里使用简单的递归。 该方法稍微取决于子对象附着到父对象的方式

如果他们在一个列表中，我建议这样做，那么这一个就可以了。 只需在类中定义以下方法：

def findObjectByName(self, name):
    if self.name == name:
        return self
    else:
        for child in self.children:
            match = child.findObjectByName(name)
            if match:
                return match
编辑： 要使此操作适用于任何属性，而不仅仅是名称，请改用
getattr（）
：

def findObject(self, attr, value):
    if getattr(self, attr) == value:
        return self
    else:
        for child in self.children:
            match = child.findObject(attr, value)
            if match:
                return match
只需调用
root.findObjectByName（“Sub-Child！”）
或使用第二种方法：
root.findObject（“name”，“Sub-Child！”）
您可以使用
递归
或使用
迭代
。无论哪种方式都无关紧要。但是你需要一个搜索树的策略

下面是一些浏览图表的策略：

其主要思想是不要两次遍历同一个节点/叶，这对于树来说很简单，但是对于图来说需要
着色
：

您可以使用一些设计模式，例如
visitor
模式，并向
TreeHierarchyClass
添加一个方法
.visit（）
，以访问其子节点，另一个方法按名称查找节点

例如：

# imagine we got this class
class TreeHierarchyClass(object):
    def __init__(self, value):
        self.children = []
        self.value = value
        if self.value == 13:
            self.name = 'the lucky one.'
    def add(self, value):
        self.children.append(type(self)(value))
您可以通过以下方式访问所有节点：

def visit(tree):
    visited = set()
    nonvisited = set()
    nonvisited.update(tree.children)
    while nonvisited:
        item = nonvisited.pop()
        # already seen
        if item in visited:
            continue
        # mark item
        visited.add(item)
        yield item
        # add children
        nonvisited.update(item.children)
让我们构建一个示例树结构：

root = TreeHierarchyClass(0)

for i in range(10):
    root.add(i)

for i in range(10):
    root.children[1].add(i + 10)
现在，让我们查找一些项目：

def find(name):
    for item in visit(root):
        print 'checking item with value %d' % item.value,
        if getattr(item, 'name', None) == name:
            print '- found it.'
            break
        else:
            print '- nope, keep searching.'
    else:
        print 'Sorry, not found.'

find('the lucky one.')
find('the lost one.')
此示例将打印：

>>> find('the lucky one.')
checking item with value 7 - nope, keep searching.
checking item with value 0 - nope, keep searching.
checking item with value 1 - nope, keep searching.
checking item with value 12 - nope, keep searching.
checking item with value 2 - nope, keep searching.
checking item with value 9 - nope, keep searching.
checking item with value 19 - nope, keep searching.
checking item with value 3 - nope, keep searching.
checking item with value 11 - nope, keep searching.
checking item with value 4 - nope, keep searching.
checking item with value 14 - nope, keep searching.
checking item with value 5 - nope, keep searching.
checking item with value 6 - nope, keep searching.
checking item with value 15 - nope, keep searching.
checking item with value 8 - nope, keep searching.
checking item with value 16 - nope, keep searching.
checking item with value 13 - found it.
>>> find('the lost one.')
checking item with value 7 - nope, keep searching.
checking item with value 0 - nope, keep searching.
checking item with value 1 - nope, keep searching.
checking item with value 12 - nope, keep searching.
checking item with value 2 - nope, keep searching.
checking item with value 9 - nope, keep searching.
checking item with value 19 - nope, keep searching.
checking item with value 3 - nope, keep searching.
checking item with value 11 - nope, keep searching.
checking item with value 4 - nope, keep searching.
checking item with value 14 - nope, keep searching.
checking item with value 5 - nope, keep searching.
checking item with value 6 - nope, keep searching.
checking item with value 15 - nope, keep searching.
checking item with value 8 - nope, keep searching.
checking item with value 16 - nope, keep searching.
checking item with value 13 - nope, keep searching.
checking item with value 17 - nope, keep searching.
checking item with value 10 - nope, keep searching.
checking item with value 18 - nope, keep searching.
Sorry, not found.
您可以使用
递归
，也可以使用
迭代
。无论哪种方式都无关紧要。但是你需要一个搜索树的策略

下面是一些浏览图表的策略：

其主要思想是不要两次遍历同一个节点/叶，这对于树来说很简单，但是对于图来说需要
着色
：

您可以使用一些设计模式，例如
visitor
模式，并向
TreeHierarchyClass
添加一个方法
.visit（）
，以访问其子节点，另一个方法按名称查找节点

例如：

# imagine we got this class
class TreeHierarchyClass(object):
    def __init__(self, value):
        self.children = []
        self.value = value
        if self.value == 13:
            self.name = 'the lucky one.'
    def add(self, value):
        self.children.append(type(self)(value))
您可以通过以下方式访问所有节点：

def visit(tree):
    visited = set()
    nonvisited = set()
    nonvisited.update(tree.children)
    while nonvisited:
        item = nonvisited.pop()
        # already seen
        if item in visited:
            continue
        # mark item
        visited.add(item)
        yield item
        # add children
        nonvisited.update(item.children)
让我们构建一个示例树结构：

root = TreeHierarchyClass(0)

for i in range(10):
    root.add(i)

for i in range(10):
    root.children[1].add(i + 10)
现在，让我们查找一些项目：

def find(name):
    for item in visit(root):
        print 'checking item with value %d' % item.value,
        if getattr(item, 'name', None) == name:
            print '- found it.'
            break
        else:
            print '- nope, keep searching.'
    else:
        print 'Sorry, not found.'

find('the lucky one.')
find('the lost one.')
此示例将打印：

>>> find('the lucky one.')
checking item with value 7 - nope, keep searching.
checking item with value 0 - nope, keep searching.
checking item with value 1 - nope, keep searching.
checking item with value 12 - nope, keep searching.
checking item with value 2 - nope, keep searching.
checking item with value 9 - nope, keep searching.
checking item with value 19 - nope, keep searching.
checking item with value 3 - nope, keep searching.
checking item with value 11 - nope, keep searching.
checking item with value 4 - nope, keep searching.
checking item with value 14 - nope, keep searching.
checking item with value 5 - nope, keep searching.
checking item with value 6 - nope, keep searching.
checking item with value 15 - nope, keep searching.
checking item with value 8 - nope, keep searching.
checking item with value 16 - nope, keep searching.
checking item with value 13 - found it.
>>> find('the lost one.')
checking item with value 7 - nope, keep searching.
checking item with value 0 - nope, keep searching.
checking item with value 1 - nope, keep searching.
checking item with value 12 - nope, keep searching.
checking item with value 2 - nope, keep searching.
checking item with value 9 - nope, keep searching.
checking item with value 19 - nope, keep searching.
checking item with value 3 - nope, keep searching.
checking item with value 11 - nope, keep searching.
checking item with value 4 - nope, keep searching.
checking item with value 14 - nope, keep searching.
checking item with value 5 - nope, keep searching.
checking item with value 6 - nope, keep searching.
checking item with value 15 - nope, keep searching.
checking item with value 8 - nope, keep searching.
checking item with value 16 - nope, keep searching.
checking item with value 13 - nope, keep searching.
checking item with value 17 - nope, keep searching.
checking item with value 10 - nope, keep searching.
checking item with value 18 - nope, keep searching.
Sorry, not found.
根目录是什么类型的对象<代码>列表<代码>指令？我不知道有什么Python语法可以像您当前的示例中那样支持子声明，如
root=[parent=[…
。什么类型的对象是
root
？
list
？
dict
？我不知道有什么Python语法可以支持子声明，如
root=[parent=[…
正如您当前在示例中所做的那样。谢谢您，我使用
child
而不是
children
，但我认为孩子更好，请更改它！谢谢您，我使用
child
而不是
children
但我认为孩子更好，请更改它！