[英]What's wrong with my python Tree
I'm trying to implement a tree structure, but when I'm trying to print data out in my tree, unexpected results are shown. 我正在尝试实现树结构,但是当我尝试在树中打印数据时,会显示意外的结果。
Correct result will be : 正确的结果将是:
root
- A1
-- A2
--- A3
---- A4
----- A5
But I got : 但是我得到了:
root
- A1
-- A1
--- A2
~ infinite loop
What's wrong with my code? 我的代码有什么问题? Can you answer me?
你可以回答我吗?
#!/usr/bin/python
class TreeNode :
def __init__(self,key,obj=dict()) :
print 'Node with '+key+' is created'
self.key=key
self.child=obj
def add_child(self, key, obj) :
self.child[key]=obj
print 'child len ',
print len(self.child)
def get_child(self) :
for key in self.child.keys() :
print key,
pass
print ''
return self.child
def find_child(self,key) :
return self.child[key]
def is_leap(self) :
print 'is_leap ',
print len(self.child)
if len(self.child)==0 :
return 1
else : return 0
def append_rec(self,hier,data,depth) :
# hier & data are lists
if len(hier)== 1 :
print 'end of hierachy. append complete @ depth ',
print depth
return
tmp = hier[0]
tmp_child = hier[1:]
name = str(hier[0])
print 'self ',
print tmp,
print 'childs ',
print tmp_child
child_list = self.get_child()
if child_list != None :
if not name in child_list.keys() :
lc = TreeNode(name)
self.add_child(name,lc)
return lc.append_rec(hier[1:],data,depth+1)
else :
lc =child_list[name]
return lc.append_rec(hier[1:],data,depth+1)
def print_all(self,depth) :
for i in range(depth) : print '-',
print self.key
if len(self.child) == 0 : return
if depth > 10 :
print 'depth limit over'
return
else :
for k in self.child.keys() :
print 'Looking child having key = '+k
return (self.child[k]).print_all(depth+1)
# recursive method
class Tree :
index = 0
# root node of tree
def __init__(self) :
self.root=TreeNode('root')
self.index=0
def get_child(self) :
return self.root.get_child()
def print_all(self) :
self.root.print_all(0)
def traverse(self) :
node=self.root
depth=0
childs = node.get_child()
if node.is_leap() : return
else :
for c in childs.keys() :
print c,
return self.traverse_rec(childs[c],depth+1)
print ' end'
def traverse_rec(self,node,depth) :
i=0
print 'depth ',
print i,
childs = node.get_child()
if node.is_leap() : return
else :
for c in childs.keys() :
print c,
return self.traverse_rec(childs[c],depth+1)
print ' end'
def append(self,tup) :
# root
tmp = tup[0].split('/')
data = tup[1]
print 'root ['+data+']',
tmp_child = tmp[1:]
name = str(tmp[0])
# if treenode with name tmp[0]
child_list = self.root.get_child()
if child_list != None :
if not name in child_list.keys() :
#print 'name = '+name
lc = TreeNode(name)
self.root.add_child(name,lc)
lc.append_rec(tmp_child,data,1)
else :
lc=child_list[name]
lc.append_rec(tmp_child,data,1)
tree = Tree()
test_string = ('A1/A2/A3/A4/A5','example1')
tree.append(test_string)
tree.print_all()
In Python, default arguments are only evaluated once. 在Python中,默认参数仅计算一次。 So each time you create a
TreeNode
without an explicit obj
argument, it gets assigned to the same dict. 因此,每次创建不带显式
obj
参数的TreeNode
,它将被分配给相同的字典。
One way to get around this is to use None as a default argument instead, like so. 解决此问题的一种方法是改为使用None作为默认参数。
def __init__(self,key,obj=None) :
print 'Node with '+key+' is created'
self.key=key
self.child=obj if obj is not None else {}
Another option is to do a defensive copy. 另一种选择是进行防御性复制。 This will help in cases where you accidentally pass it a dict by reference when you don't want to, though this means that it may mask other bugs.
如果您不希望通过引用将其作为字典,这将很有帮助,尽管这意味着它可能掩盖了其他错误。 Also note that this will only do a shallow copy, which is usually what you want, but not always.
另请注意,这只会进行浅表复制,通常这是您想要的,但并非总是如此。
def __init__(self,key,obj=dict()) :
print 'Node with '+key+' is created'
self.key=key
self.child=obj.copy()
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