好像比較懂你的意思了, 試寫了一個 Tree, 不知道你覺得怎麼樣XD

class Tree:

def __init__(self, name):

self.name = name

self.children = {}

def __iter__(self):

return iter(self.children)

def __str__(self):

return self.name

def __repr__(self):

return 'Tree("{}")'.format(self.name)

def relationiter(self):

yield from self.children.items()

def add_child(self, child, relation):

self.children[child] = relation

return child

def dfs(self, include_self=True):

if include_self:

yield self

for child in self.children:

yield child

yield from child.dfs(False)

def bfs(self, include_self=True):

if include_self:

yield self

trees = list(self.children.keys())

while True:

if not trees:

break

tree = trees.pop(0)

yield tree

trees += list(tree.children.keys())

import and create tree:

In [1]: from tree import Tree

In [2]: root = Tree('root')

...:

...: t11 = root.add_child(Tree('t11'), 30)

...: t12 = root.add_child(Tree('t12'), 40)

...:

...: t21 = t11.add_child(Tree('t21'), 15)

...: t22 = t11.add_child(Tree('t22'), 10)

...: t23 = t11.add_child(Tree('t23'), 35)

...:

...: t24 = t12.add_child(Tree('t24'), 20)

...:

測試 __str__ 跟 __repr__:

In [3]: root

Out[3]: Tree("root")

In [4]: print(root)

root

測試 iterator 和 relation iterator:

In [5]: for child in root:

...: print(child)

...:

t12

t11

In [6]: for child, relation in root.relationiter():

...: print(child, relation)

...:

t12 40

t11 30

測試 dfs 和 bfs:

In [7]: for tree in root.dfs(include_self=True):

...: print(tree)

...:

root

t12

t24

t11

t21

t22

t23

In [8]: for tree in root.bfs(include_self=True):

...: print(tree)

...:

root

t12

t11

t24

t21

t22

t23

這邊還有一個問題是, 不知道你原始的資料長甚麼樣子, 所以我無法猜測你怎麼 create tree。

如果是手動一個一個加入 child 的話應該就像上面那樣, create 跟 recursion 沒什麼關係, traverse 的時候才跟 recursion 有關。

除非你有一個對應於 tree 結構的資料, 字典, json 之類的, 然後你想要依資料自動生成, 可能這種情況才會用 recursion 來 build tree。

因為我對於你實際的輸入不是很了解, 但是我猜你想問的是下面這件事情, 我舉個想像的例子說明這一點, 假設我們的原始資料長這樣:

data = {

't11': {

'relation': 30,

'sub': {

't21': {

'relation': 15

},

't22': {

'relation': 10

},

't23': {

'relation': 35

}

}

},

't12': {

'relation': 40,

'sub': {

't24': {

'relation': 20

},

}

}

}

我必須要將這樣子的資料建出一個 Tree 來, 這邊的確就跟 recursion 有關了, 首先我在 Tree 中增加一個 classmethod:

@classmethod

def from_data(cls, name, data):

tree = cls(name)

if data:

for subname, subdata in data.items():

tree.add_child(

cls.from_data(subname, subdata.get('sub', None)),

subdata['relation'])

return tree

接著我可以用下面這種方式 recursive 地 create tree:

root = Tree.from_data('root', data)

測試:

for tree in root.bfs():

print(tree)

for child, relation in tree.relationiter():

print(' {}-{}'.format(child, relation))

結果:

root

t12-40

t11-30

t12

t24-20

t11

t21-15

t23-35

t22-10

t24

t21

t23

t22

P.S. 有問題歡迎討論!