请教关于引用的一个问题

[xiaoyan94]

a
[9, 7, 5, 3, 1]
b
[9, 7, 5, 3, 1]
a.reverse()
a
[1, 3, 5, 7, 9]
b
[1, 3, 5, 7, 9] #为什么这里b也会变？

[lambdaplus]

---

In [13]: a = [9, 7, 5, 3, 1]

In [14]: b = a

In [15]: b
Out[15]: [9, 7, 5, 3, 1]

In [16]: a.reverse()

In [17]: a
Out[17]: [1, 3, 5, 7, 9]

In [18]: b
Out[18]: [1, 3, 5, 7, 9]

上面的a和b其实是指向的同一个内存地址，修改任一个的值，都会影响到另一个。

In [26]: a.__str__
Out[26]: <method-wrapper '__str__' of list object at 0x7fc1f7f68988>

In [27]: b.__str__
Out[27]: <method-wrapper '__str__' of list object at 0x7fc1f7f68988>

---

下面是n是m的拷贝，m、n内存地址不同。

In [24]: m.__str__
Out[24]: <method-wrapper '__str__' of list object at 0x7fc1f7f6fdc8>

In [25]: n.__str__
Out[25]: <method-wrapper '__str__' of list object at 0x7fc1f7e6bdc8>

In [19]: m = [0, 2, 4, 6, 8]

In [20]: n = m.copy()

In [21]: m.reverse()

In [22]: m
Out[22]: [8, 6, 4, 2, 0]

In [23]: n
Out[23]: [0, 2, 4, 6, 8]

再深一点就是__深拷贝和浅拷贝__了
个人愚见。

[qiwsir]

有道理。很多高级语言，都是将某些基本类型和由基本类型组合的类型，以不同的存储方式处理。

2016-05-05 17:04 GMT+08:00 lambdaplus [email protected]:

---

In [13]: a = [9, 7, 5, 3, 1]

In [14]: b = a

In [15]: b
Out[15]: [9, 7, 5, 3, 1]

In [16]: a.reverse()

In [17]: a
Out[17]: [1, 3, 5, 7, 9]

In [18]: b
Out[18]: [1, 3, 5, 7, 9]

上面的a和b其实是指向的_同一个内存地址_，修改任一个的值，都会影响到另一个。

In [26]: a.str
Out[26]: <method-wrapper 'str' of list object at 0x7fc1f7f68988>

In [27]: b.str
Out[27]: <method-wrapper 'str' of list object at 0x7fc1f7f68988>

---

下面是n是m的拷贝，m、n内存地址不同。

In [24]: m.str
Out[24]: <method-wrapper 'str' of list object at 0x7fc1f7f6fdc8>

In [25]: n.str
Out[25]: <method-wrapper 'str' of list object at 0x7fc1f7e6bdc8>

In [19]: m = [0, 2, 4, 6, 8]

In [20]: n = m.copy()

In [21]: m.reverse()

In [22]: m
Out[22]: [8, 6, 4, 2, 0]

In [23]: n
Out[23]: [0, 2, 4, 6, 8]

再深一点就是__深拷贝和浅拷贝__了
个人愚见。

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#98 (comment)

QiWei

[xiaoyan94]

谢谢！