On the strange phenomenon of Python objects

Declared a node class ：

class Node:
feat = -1
child = []
label = -1
def __init__(self, feat, label):
self.feat = feat
self.label = label

Create two node, And will node2 Put in node1 Medium child in ：

node1 = Node(2, 0)
node2 = Node(3, 1)
print(node2.feat, node2.label)
node2.change(9)
node1.child.append(node2)
print(len(node1.child))
print(node1.child[0].feat, node1.child[0].label)
Output results :
3 1
1
9 1

When redefining two different initial values node, Same operation , But found node1 Of child The number becomes 2

node1 = Node(2, 2)
node2 = Node(6, 1)
print(node2.feat, node2.label)
node2.change(15)
node1.child.append(node2)
print(len(node1.child))
print(node1.child[0].feat, node1.child[0].label)

Traverse node1.child After the discovery , Two node2 It's all in it ：

for i in range(len(node1.child)):
print(node1.child[i].feat, node1.child[i].label)
Output results :
9 1
15 1