关于python：在这两种情况下，对象的这个属性是如何成为不同的值的？

How is this property of an object a different value in these two cases?

本问题已经有最佳答案，请猛点这里访问。

如何调用列表(Case 1的属性，使print y的输出与Case 2的输出不同？

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# Case 1: using a list as value
>>> x = ["one","two","three"]
>>> y = x
>>> x[0] ="four"
>>> print x
["four","two","three"]
>>> print y
["four","two","three"]

# Case 2: using an integer as value
>>> x = 3
>>> y = x
>>> x = x + 1
>>> print x
4
>>> print y
3

编辑：

为了证明这种行为与列表是可变的和字符串无关，而不是案例2，可以给出以下案例：

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>>> x = ["one","two","three"]
>>> y = x
>>> x = x + ["four","five"]
>>> print x
["four","two","three","four","five"]
>>> print y
["four","two","three"]

相关讨论

两个片段之间的关键区别是

1	>>> x[0] ="four"

1	>>> x = x + 1

在第一种情况下，修改现有对象，在第二种情况下创建新对象。所以第一个片段有一个对象和两个名称x和y，引用它，在第二个片段中有两个对象。注意，这与列表的可变性(和int的不可变性)无关，您可以将第二个代码段编写为

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x = [1,2,3]
y = x
x = x + [4]

得到基本相同的结果(=两个不同的物体)。