Python Stack Corruption？(Python Stack Corruption?)

 我是python的新手（但不是编程），我无法解释以下行为。 似乎一个对象（“child”）中的变量（我的示例中的列表“children”）被一个完全不同的对象（“node”）中的该变量的值覆盖。 为了给出一些上下文，我正在尝试创建一个在树结构中使用的简单Node类。 该节点具有子节点和父节点（所有其他节点）。 
 
 我无法弄清楚为什么child.children获得与node.children相同的值。 他们以某种方式引用相同的数据吗？ 为什么？ 代码和输出如下： 
 
class Node:
    children = []
    parent = 0
    visited = 0
    cost = 0
    position = (0, 0)
    leaf = 0

    def __init__(self, parent, pos):
        self.parent = parent
        self.position = pos

    def addChild(self, node):
        self.children += [node]

node = Node(0, (0,0))
child = Node(node, (3,2))

node.addChild(child)

print "node: ",
print node

print "node.childen: ",
print node.children

print "child: ",
print child

print "child.children",
print child.children
 
 输出： 
 
node:  <__main__.Node instance at 0x414b20>
node.childen:  [<__main__.Node instance at 0x414b48>]
child:  <__main__.Node instance at 0x414b48>
child.children [<__main__.Node instance at 0x414b48>]
 
 如您所见，node.children和child.children都具有相同的值（包含child的列表），即使我只更新了node.children。 谢谢你的帮助！ 

I'm relatively new to python (but not to programming), and I can't explain the following behavior. It appears that a variable (the list "children" in my example) from one object ("child") is getting overwritten by the value for that variable in a completely different object ("node"). To give some context, I'm trying to create a simple Node class to use in a tree structure. The node has children and a parent (all other nodes).
 
I can't figure out why child.children gets the same value as node.children. Are they somehow referencing the same data? Why? Code and output follows:
 
class Node:
    children = []
    parent = 0
    visited = 0
    cost = 0
    position = (0, 0)
    leaf = 0

    def __init__(self, parent, pos):
        self.parent = parent
        self.position = pos

    def addChild(self, node):
        self.children += [node]

node = Node(0, (0,0))
child = Node(node, (3,2))

node.addChild(child)

print "node: ",
print node

print "node.childen: ",
print node.children

print "child: ",
print child

print "child.children",
print child.children
 
Output:
 
node:  <__main__.Node instance at 0x414b20>
node.childen:  [<__main__.Node instance at 0x414b48>]
child:  <__main__.Node instance at 0x414b48>
child.children [<__main__.Node instance at 0x414b48>]
 
As you can see, both node.children and child.children have the same value (a list containing child) even though I only updated node.children. Thanks for any help!

原文：https://stackoverflow.com/questions/8627628