深浅拷贝

Posted 2021-11-27 little-raccoon

lst1 = ["金毛狮王", "紫衫龙王", "白眉鹰王", "青翼蝠王"]
lst2 = lst1
print(lst1)
print(lst2)
lst1.append("杨逍")
print(lst1)
print(lst2)
# 结果:
# [‘金毛狮王‘, ‘紫衫龙王‘, ‘白眉鹰王‘, ‘青翼蝠王‘, ‘杨逍‘]
# [‘金毛狮王‘ ‘紫衫龙王‘ ‘白眉鹰王‘ ‘青翼蝠王‘ ‘杨逍‘]

dic1 = {"id": 123, "name": "谢逊"}
dic2 = dic1
print(dic1)
print(dic2)
dic1[‘name‘] = "范瑶"
print(dic1)
print(dic2)
# 结果:
# {‘id‘: 123, ‘name‘: ‘谢逊‘}
# {‘id‘: 123, ‘name‘: ‘谢逊‘}
# {‘id‘: 123, ‘name‘: ‘范瑶‘}
# {‘id‘: 123, ‘name‘: ‘范瑶‘}

对于list, set, dict来说, 直接赋值. 其实是把内存地址交给变量. 并不是复制一份内容. 所以.
lst1的内存指向和lst2是一样的. lst1改变了, lst2也发生了改变

 

浅拷贝

lst1 = ["何炅", "杜海涛","周渝民"]
lst2 = lst1.copy()
lst1.append("李嘉诚")
print(lst1)  # [‘何炅‘, ‘杜海涛‘, ‘周渝民‘, ‘李嘉诚‘]
print(lst2)  # [‘何炅‘, ‘杜海涛‘, ‘周渝民‘]
print(id(lst1), id(lst2))   # 43601416 43473160

结果:
两个lst完全不一样. 内存地址和内容也不一样. 发现实现了内存的拷贝

lst1 = ["何炅", "杜海涛","周渝民", ["麻花藤", "马芸", "周笔畅"]]
lst2 = lst1.copy()
lst1[3].append("无敌是多么寂寞")
print(lst1)
print(lst2)
print(id(lst1[3]), id(lst2[3]))
# 结果:
# [‘何炅‘, ‘杜海涛‘, ‘周渝民‘, [‘麻花藤‘, ‘马芸‘, ‘周笔畅‘, ‘无敌是多么寂寞‘]]
# [‘何炅‘, ‘杜海涛‘, ‘周渝民‘, [‘麻花藤‘, ‘马芸‘, ‘周笔畅‘, ‘无敌是多么寂寞‘]]
# 4417248328 4417248328

浅拷贝. 只会拷贝第一层. 第二层的内容不会拷贝. 所以被称为浅拷贝

 

深拷贝

import copy
lst1 = ["何炅", "杜海涛","周渝民", ["麻花藤", "马芸", "周笔畅"]]
lst2 = copy.deepcopy(lst1)
lst1[3].append("无敌是多么寂寞")
print(lst1)
print(lst2)
print(id(lst1[3]), id(lst2[3]))
# 结果:
# [‘何炅‘, ‘杜海涛‘, ‘周渝民‘, [‘麻花藤‘, ‘马芸‘, ‘周笔畅‘, ‘无敌是多么寂寞‘]]
# [‘何炅‘, ‘杜海涛‘, ‘周渝民‘, [‘麻花藤‘, ‘马芸‘, ‘周笔畅‘]]
# 4447221448 4447233800

可见深拷贝是把元素内部的元素完全进行拷贝复制，不会产生一个改变另一个跟着改变的问题