1、淺拷貝和深拷貝

淺拷貝復(fù)制指向某個(gè)對(duì)象的地址（指針），而不復(fù)制對(duì)象本身，新對(duì)象和原對(duì)象共享同一內(nèi)存。

深拷貝會(huì)額外創(chuàng)建一個(gè)新的對(duì)象，新對(duì)象跟原對(duì)象并不共享內(nèi)存，修改新對(duì)象不會(huì)影響到原對(duì)象。

賦值其實(shí)就是引用了原對(duì)象。兩者指向同一內(nèi)存，兩個(gè)對(duì)象是聯(lián)動(dòng)的，無(wú)論哪個(gè)對(duì)象發(fā)生改變都會(huì)影響到另一個(gè)。

2、直接賦值

使用=來(lái)復(fù)制一個(gè)列表，實(shí)際上不僅復(fù)制了其中的內(nèi)容，也復(fù)制了其內(nèi)存地址，即引用了原列表。使用id()方法查看內(nèi)存地址也是一樣的。修改其中一個(gè)列表，也會(huì)直接更改另一個(gè)列表。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    # 直接復(fù)制，即引用列表
    b = a
    print(a)
    print(b)
    # 通過(guò)id()查看內(nèi)存地址，為一樣的
    print(id(a), id(b))
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
2030264836936 2030264836936
['g', ['f', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

3、for循環(huán)

使用for循環(huán)進(jìn)行拷貝，僅第一層為深拷貝，對(duì)其它層依然是淺拷貝。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    b = []
    # 使用for循環(huán)進(jìn)行拷貝，僅第一層為深拷貝
    for i in a:
        b.append(i)
    print(a)
    print(b)
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['f', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

4、切片

使用切片方法進(jìn)行拷貝，也僅對(duì)第一層為深拷貝，對(duì)其它層依然是淺拷貝。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    # 使用切片進(jìn)行拷貝，僅第一層為深拷貝
    b = a[:]
    print(a)
    print(b)
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['f', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

5、copy()方法

（1）list.copy()方法

使用list.copy()方法進(jìn)行拷貝，也僅對(duì)第一層為深拷貝，對(duì)其它層依然是淺拷貝。由于列表中嵌套的列表實(shí)際保存的是地址，依然指向同一個(gè)內(nèi)存地址。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    # 使用list.copy()方法進(jìn)行拷貝，僅第一層為深拷貝
    b = a.copy()
    print(a)
    print(b)
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['f', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

（2）copy.copy()方法

使用copy.copy()方法進(jìn)行拷貝，也僅對(duì)第一層為深拷貝，對(duì)其它層依然是淺拷貝。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import copy
 
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    # 使用copy.copy()方法進(jìn)行拷貝，僅第一層為深拷貝
    b = copy.copy(a)
    print(a)
    print(b)
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['f', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

6、deepcopy()方法

使用copy.deepcopy()方法進(jìn)行拷貝，對(duì)所有層均為深拷貝，改變新列表并不會(huì)影響到原列表，推薦使用。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import copy
 
if __name__ == '__main__':
    a = ["a", ["b", "c", "d"], ["e", "f"]]
    # 使用copy.deepcopy()方法進(jìn)行拷貝，對(duì)所有層均為深拷貝
    b = copy.deepcopy(a)
    print(a)
    print(b)
    b[0] = "g"
    b[1][0] = "f"
    print(a)
    print(b)

輸出：

['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['a', ['b', 'c', 'd'], ['e', 'f']]
['g', ['f', 'c', 'd'], ['e', 'f']]
 
Process finished with exit code 0

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