深浅拷贝与赋值

参考：http://www.cnblogs.com/Eva-J/p/5534037.html

对于 数字 和 字符串 而言，赋值、浅拷贝和深拷贝无意义，因为其永远指向同一个内存地址。（可以把数字，字符串看作是内存中最小的地址）

对于字典、元祖、列表 而言，进行赋值、浅拷贝和深拷贝时，其内存地址的变化是不同的。浅拷贝只拷贝第一层地址，而深拷贝是不管你数据结构多么复杂，都在内存里开辟一块新的空间，直到简单数据类型为止。

以这个字典为例：

dict = {"k1":"mu","k2":23,"k3":["alex",123]}

dict = {"k1":"mu","k2":23,"k3":["alex",123]}
dict1=dict
print(id(dict))
print(id(dict1))
输出结果：
2243042460872
2243042460872

import copy
dict = {"k1":"mu","k2":23,"k3":["alex",123]}
dict2=copy.copy(dict)
print(id(dict))
print(id(dict2))
print(id(dict[‘k3‘]))
print(id(dict2[‘k3‘]))
输出结果：
2053865129160
2053865571208
2053867015560
2053867015560

import copy
dict = {"k1":"mu","k2":23,"k3":["alex",123]}
dict3 = copy.deepcopy(dict)
print(id(dict))
print(id(dict3))
print(id(dict[‘k3‘]))
print(id(dict3[‘k3‘]))
输出结果：
3045244716232
3045245124744
3045246601736
3045246600456

深浅copy的应用举例：

 1 import copy
 2 dic = {
 3     "cpu":[80,],
 4     "mem":[80,],
 5     ‘disk‘:[80,]
 6 }
 7 print(‘before:‘,dic)
 8 new_dic = copy.copy(dic)
 9 new_dic[‘cpu‘][0] = 50
10 print(dic)
11 print(new_dic)
12 输出结果：
13 before: {‘disk‘: [80], ‘cpu‘: [80], ‘mem‘: [80]}
14 {‘disk‘: [80], ‘cpu‘: [50], ‘mem‘: [80]}
15 {‘disk‘: [80], ‘cpu‘: [50], ‘mem‘: [80]}

浅copy

 1 import copy
 2 dic = {
 3     "cpu":[80,],
 4     "mem":[80,],
 5     ‘disk‘:[80,]
 6 }
 7 print(‘before:‘,dic)
 8 new_dic = copy.deepcopy(dic)
 9 new_dic[‘cpu‘][0] = 50
10 print(dic)
11 print(new_dic)
12 输出结果：
13 before: {‘cpu‘: [80], ‘mem‘: [80], ‘disk‘: [80]}
14 {‘cpu‘: [80], ‘mem‘: [80], ‘disk‘: [80]}
15 {‘cpu‘: [50], ‘mem‘: [80], ‘disk‘: [80]}

深copy