Python对象赋值浅拷贝深拷贝

Posted 2021-12-24 bqwzx

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Python中，基本数据类型，理解为常见数据类型：布尔型、整型、浮点型、字符串、列表、元组、字典、集合，随语言不同而不同，但是根据在内存中存储方式的不同，区分开原子类型和容器类型。

对象赋值

对象的赋值都是进行（对象引用传递）/（内存地址传递）/(内存引用），所以当一个对象改变，另一个同步改变。

结合代码思考
···
will = ["Will", 28, ["Python", "C#", "javascript"]] # 元素的数据类型有原子类型和容器类型
wilber = will
print id(will) # will的id
print will
print [id(ele) for ele in will] # will中每个元素的id
print id(wilber) # wilber的id == will的id
print wilber

will[0] = "Wilber" # 改动will中的元素0
will[2].append("CSS") # 改动will中的元素2
print id(will) # will的id没变
print will
print [id(ele) for ele in will]
print id(wilber) # wilber
print wilber
print [id(ele) for ele in wilber]
···

浅拷贝

浅拷贝对象是容器类型，原子类型只有对象赋值。浅拷贝会新起一个对象，将原容器包含的内存地址引用过去。当原容器包含的元素有可变的（即容器对象），容器元素的改变也会引起新拷贝对象内元素的改变。

结合代码思考

import copy

will = ["Will", 28, ["Python", "C#", "JavaScript"]]
wilber = copy.copy(will)

print id(will)
print will
print [id(ele) for ele in will]
print id(wilber)
print wilber
print [id(ele) for ele in wilber]

will[0] = "Wilber"
will[2].append("CSS")
print id(will)
print will
print [id(ele) for ele in will]
print id(wilber)
print wilber
print [id(ele) for ele in wilber]

深拷贝

深拷贝对象也是容器类型，原子类型只有对象赋值。深拷贝和浅拷贝一样，也会根据原对象深拷贝新起一个对象，但是会将元素里面的容器类型的新拷贝一份（默认深入新拷贝层数好像是1），因此原对象的容器元素改变了，新对象的容器元素不会改变。

结合代码思考

import copy

will = ["Will", 28, ["Python", "C#", "JavaScript"]]
wilber = copy.deepcopy(will)

print id(will)
print will
print [id(ele) for ele in will]
print id(wilber)
print wilber
print [id(ele) for ele in wilber]

will[0] = "Wilber"
will[2].append("CSS")
print id(will)
print will
print [id(ele) for ele in will]
print id(wilber)
print wilber
print [id(ele) for ele in wilber]

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总结

数据结构+算法，需要反复学习+理解+记忆。

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https://www.cnblogs.com/wilber2013/p/4645353.html#_nav_1