Обнаружил странную проблему при написании b+деревьев с использованием Python. ⇐ Python

[Гость]

Tree node structure:

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class BPlusNode:
def __init__(self,isleaf = True,val=[],parent=None,children=[]):
self.values = val
self.children = children
self.parent = parent
self.isleaf = isleaf
self.order=3

where the bug appears:

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def split(self,node):
if (len(node.children)==0 and len(node.values) 5):
sys.exit()
print('',new_root.values)

node.parent=new_root
self.root=new_root
parent=new_root

input 3,1,4,5 in order
the output is:
the output
strangely the new node has already been assigned values
but the program runs correctly if I write like this:

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new_root=BPlusNode(isleaf=False,val=[],parent=None,children=[])

Why does this happens?
I noticed a mechanism of default parameter in python:
operations on mutable objects with default parameters will be preserved
for example:

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cnt=2
def f(data=[]):
global cnt
data.append(1)
print(data)
data[0]=cnt
cnt+=1
return data
f()
f()
f()

the output will be:

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[1]
[2, 1]
[3, 1, 1]

but in my code:

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def __init__(self,isleaf = True,val=[],parent=None,children=[]):

the parameter "val" has not been operated
Is this problem related to this mechanism?
Or it is caused by other reasons?


Источник: https://stackoverflow.com/questions/781 ... ing-python