import copy a = "deepak" b = 1, 2, 3, 4 c = [1, 2, 3, 4] d = {1: 10, 2: 20, 3: 30} a1 = copy.copy(a) b1 = copy.copy(b) c1 = copy.copy(c) d1 = copy.copy(d) print("immutable - id(a)==id(a1)", id(a) == id(a1)) print("immutable - id(b)==id(b1)", id(b) == id(b1)) print("mutable - id(c)==id(c1)", id(c) == id(c1)) print("mutable - id(d)==id(d1)", id(d) == id(d1))
我得到以下结果:
immutable - id(a)==id(a1) True immutable - id(b)==id(b1) True mutable - id(c)==id(c1) False mutable - id(d)==id(d1) False
如果我执行深度复制:
a1 = copy.deepcopy(a) b1 = copy.deepcopy(b) c1 = copy.deepcopy(c) d1 = copy.deepcopy(d)
结果是相同的:
如果我从事分配作业:
a1 = a b1 = b c1 = c d1 = d
那么结果是:
immutable - id(a)==id(a1) True immutable - id(b)==id(b1) True mutable - id(c)==id(c1) True mutable - id(d)==id(d1) True
有人可以解释究竟是什么造成了副本之间的差异吗?它和可变且不可变的对象有关吗?如果是这样,您能给我解释一下吗?
普通赋值操作将简单地将新变量指向现有对象。该文档解释了浅拷贝和深拷贝之间的区别:
浅表复制和深度复制之间的区别仅与复合对象(包含其他对象的对象,如列表或类实例)有关:
浅表副本构造一个新的复合对象,然后(在可能的范围内)将对原始对象中引用的对象的引用插入其中。
深层副本会构造一个新的复合对象,然后递归地将原始对象中发现的对象的副本插入其中。
这是一个小示范:
import copy a = [1, 2, 3] b = [4, 5, 6] c = [a, b]
使用常规分配操作进行复制:
d = c print id(c) == id(d) # True - d is the same object as c print id(c[0]) == id(d[0]) # True - d[0] is the same object as c[0]
使用浅表副本:
d = copy.copy(c) print id(c) == id(d) # False - d is now a new object print id(c[0]) == id(d[0]) # True - d[0] is the same object as c[0]
使用深拷贝:
d = copy.deepcopy(c) print id(c) == id(d) # False - d is now a new object print id(c[0]) == id(d[0]) # False - d[0] is now a new object