Python的深拷贝
1、打开电脑的运行输入‘cmd’，在弹出的命令行窗口输入‘python’
2、在python交互命令行输入以下内容：Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 17:00:18) [MSC v.1900 64 bit (AMD64)] on win32Type "help", "copyright", "credits" or "license" for more information.>>> import copy>>> ll=['a','b']>>> list1=['x',ll]>>> print (list1)['x', ['a', 'b']]>>> list2 = copy.deepcopy(list1)>>> print (list2)['x', ['a', 'b']]>>>list1和list2内容完全一样，ll是嵌套的列表
3、list1添加元素不会影响list2,测试代码如下：>>> import copy>>> ll=['a','b']>>> list1=['x',ll]>>> print (list1)['x', ['a', 'b']]>>> list2 = copy.deepcopy(list1)>>> print (list2)['x', ['a', 'b']]>>> list1.append('new')>>> print (list1)['x', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>>
4、list1修改元素不会影响list2,测试代码如下：>>> import copy>>> ll=['a','b']>>> list1=['x',ll]>>> print (list1)['x', ['a', 'b']]>>> list2 = copy.deepcopy(list1)>>> print (list2)['x', ['a', 'b']]>>> list1.append('new')>>> print (list1)['x', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> list1[0]='0'>>> print (list1)['0', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>>
5、嵌套列表ll的修改也只会影响list1,不会影响list2巳呀屋饔,代码如下：>>> import copy>>> ll=['a','芟鲠阻缒b']>>> list1=['x',ll]>>> print (list1)['x', ['a', 'b']]>>> list2 = copy.deepcopy(list1)>>> print (list2)['x', ['a', 'b']]>>> list1.append('new')>>> print (list1)['x', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> list1[0]='0'>>> print (list1)['0', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> ll[0] = 'change'>>> print (list1)['0', ['change', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>>
6、嵌套列表ll的添加元素也只会影响list1,不会影响list2,代码如下：>>> import copy>>媪青怍牙> ll=['a','b']>>> list1=['x',ll]>>> print (list1)['x', ['a', 'b']]>>> list2 = copy.deepcopy(list1)>>> print (list2)['x', ['a', 'b']]>>> list1.append('new')>>> print (list1)['x', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> list1[0]='0'>>> print (list1)['0', ['a', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> ll[0] = 'change'>>> print (list1)['0', ['change', 'b'], 'new']>>> print (list2)['x', ['a', 'b']]>>> ll.append('aa')>>> print (list1)['0', ['change', 'b', 'aa'], 'new']>>> print (list2)['x', ['a', 'b']]>>>
7、这是因为深拷贝不同于浅拷贝，浅拷贝如果有嵌套，嵌套内容的更改会同时影响到拷贝方和被拷贝方，因为指向同一个地址，而深拷贝其实是另外开辟了内存空间，和原来的内容完全一致，但是互相独立。