python基础之深浅拷贝

深浅拷贝：

对于字符串（str）,数字（int）,布尔类型（bool）等类型深浅拷贝都是开辟新内存

对于列表（list）,集合（set）,字典（dict）深浅拷贝可变类型都一样，如[1,2,3]
对于列表（list）,集合（set）,字典（dict）存在嵌套的深浅拷贝不一样，如[1,2,3,[4,5,6]]，浅拷贝只拷贝[1,2,3],深拷贝[1,2,3,[4,5,6]]

浅拷贝：拷贝第一层
深拷贝：拷贝所有数据（可变）

应该每次都拷贝一份（但由于小数据池，未拷贝）
v = 'sundy'
import copy
v1 = copy.copy(v)
v2 =copy.deepcopy(v)
print(id(v),id(v1))
print(id(v),id(v2))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
1761132524464 1761132524464
1761132524464 1761132524464

v = [1,2,3,4]
import copy
v1 = copy.copy(v)
v2 =copy.deepcopy(v)
print(id(v),id(v1))
print(id(v),id(v2))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
2561119066504 2561120559432
2561119066504 256112055962

浅拷贝：

v = [1,2,3,4,[5,6,7]]
import copy
v1 = copy.copy(v)
print(v == v1)
print(v is v1)
print(v[4] == v1[4])
print(v[4] is v1[4])

D:python3.6python3.6.exe D:/python_code/day01/day06.py
True
False
True
True

 

 

v = [1,2,3,4,[5,6,7]]
import copy
v1 = copy.copy(v) #浅拷贝只拷贝空壳[]

print(id(v),id(v1))
print(id(v[2]),id(v1[2]))
print(id(v[4]),id(v1[4]))

 

D:python3.6python3.6.exe D:/python_code/day01/day06.py
1978756340040 1978757833096
1689026736 1689026736
1978756340104 1978756340104

 

#深拷贝

v = [1,2,3,4,[5,6,7]]
import copy
v1 = copy.deepcopy(v)
print(v == v1)
print(v is v1)
print(v[4] == v1[4])
print(v[4] is v1[4])

D:python3.6python3.6.exe D:/python_code/day01/day06.py
True
False
True
False

 

 

v2 =copy.deepcopy(v)#深拷贝拷贝嵌套里面空壳[](即可变类型)
print(id(v),id(v2))
print(id(v[2]),id(v2[2]))
print(id(v[4]),id(v2[4]))
print(id(v[4][1]),id(v2[4][1]))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
2764609460552 2764610953608
1692303536 1692303536
2764609460616 2764609460616
2764609460552 2764610953800
1692303536 1692303536
2764609460616 2764610955080
1692303632 1692303632

特殊情况：

对于不可变类型的元组深浅拷贝内存地址不变
v = (1,2,3,4,5)
import copy
v1 = copy.copy(v)
print(id(v),id(v1))
v1 = copy.deepcopy(v)
print(id(v),id(v1))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
1747241185792 1747241185792
1747241185792 1747241185792

对于不可变类型的元组存在可变类型深拷贝内存地址不一样
v = (1,2,3,4,5,[6,7,8,9])
import copy
v1 = copy.copy(v)
print(id(v),id(v1))
v1 = copy.deepcopy(v)
print(id(v),id(v1))

D:python3.6python3.6.exe D:/python_code/day01/day06.py
2430290597736 2430290597736
2430290597736 2430291562760

总结：
不可变类型：数字（int）,字符串（str）,布尔（bool）,元组（tuple）
可变类型：列表（list）,字典（dict）,集合（set）
深浅拷贝只拷贝可变类型的内存地址