Python中浅拷贝的四种实现方法小结_开发_开发者

方式一：使用切片 [:]

列表

# 浅拷贝 [:]
old_list = [1, 2, [3, 4]]
new_list = old_list[:]

old_list.append(5)
old_list[2][0] += 97

print("Old list:", old_list, "old list id:", id(old_list), " old list[0] id:", id(old_list[2]))
print("new list:", new_list, "new list id:", id(new_list), " new list[0] id:", id(new_list[2]))


# 输出结果
Old list: [1, 2, [100, 4], 5] old list id: 4537660608  old list[0] id: 4537659840
new list: [1, 2, [100, 4]] new list id: 4537711424  new list[0] id: 4537659840

方式二：使用工厂函数

工厂函数简介

工厂函数看上去像函数，但实际是一个类
调用时，生成该数据类型类型的一个实例

可变对象的工厂函数

list()
set()
dict()

列表

old_list = [1, 2, [3, 4]]
new_list = list(old_list)

old_list.append(5)
old_list[2][0] += 97

print("Old list:", old_list, "old list id:", id(old_list), " old list[0] id:", id(old_list[2]))
print("new list:", new_list, "new list id:", id(new_list), " new list[0] id:", id(newxYnPGYHxGN_list[2]))

集合

old_set = {1, 2, 3}
new_set = set(old_set)

old_set.add(4)

print("Old set:", old_set, "old set id:", id(old_set))
print("new set:", new_set, "new set id:", id(new_set))


# 输出结果
Old set: {1, 2, 3, 4} old set id: 4484723648
new set: {1, 2, 3} new set id: 4484723872

字典

old_dict = {"name": "小明"}
new_dict = dict(old_dict)

old_dict["second"] = "python"

print("Old dict:", old_dict, "old dict id:", id(old_dict))
print("new dict:", new_dict, "new dict id:", id(new_dict))


# 输出结果
Old dict: {'name': '小明', 'second': 'Python'} old dict id: 4514161536
new dict: {'name': '小明'} new dict id: 4515690304

方式三：使用数据类型自带的 copy 方法

列表

old_list = [1, 2, [3, 4]]
new_list = old_list.copy()

old_list.append(5)
www.cppcns.comold_list[2][0] += 97

print("Old list:", old_list, "old list id:", id(old_list), " old list[0] id:", id(old_list[2]))
print("new list:", new_list, "new list id:", iwww.cppcns.comd(new_list), " new list[0] id:", id(new_list[2]))


# 输出结果
Old list: [1, 2, [100, 4], 5] old list id: 4309832000  old list[0] id: 4310372992
new list: [1, 2, [100, 4]] new list id: 4309735296  new list[0] id: 4310372992

集合

old_set = {1, 2, 3}
new_set = old_set.copy()

old_set.add(4)

print("Old set:", old_set, "old set id:", id(old_set))
print("new set:", new_set, "new set id:", id(new_set))


# 输出结果
Old set: {1, 2, 3, 4} old set id: 4309931392
new set: {1, 2, 3} new set id: 4309930944

字典

old_dict = {"name": "小明"}
new_dict = old_dict.copy()

old_dict["second"] = "Python"

print("Old dict:", old_dict, "old dict id:", id(old_dict))
print("new dict:", new_dict, "new dict id:", id(new_dict))

 

# 输出结果
Old dict: {'name': '小明', 'second': 'Python'} old dict id: 4308452288
new dict: {'name': '小明'} new dict id: 4308452224

源码

    def copy(self, *args, **kwargs): # real signature unknown
        """ Return a shallow copy of the list. """
        pass

已经写的很清楚，这是浅拷贝

方式四：使用 copy 模块的 copy 方法

列表

from copy import copy

old_list = [1, 2, [3, 4]]
new_list = copy(old_list)

old_list.append(5)
old_list[2][0] += 97

print("Old list:", old_list, "old list id:", id(old_list), " old list[0] id:", id(old_list[2]))
print("new list:", new_list, "new list id:", id(new_list), " new list[0] id:", id(new_list[2]))


# 输出结果
Old list: [1, 2, [100, 4], 5] old list id: 4381013184  old list[0] id: 4381159936
new list: [1, 2, [100, 4]] new list id: 4381012800  new list[0] id: 4381159936

集合

from copy import copy

old_set = {1, 2, 3}
new_set = copy(old_set)

old_set.add(4)

print("Old set:", old_set, "old set id:", id(old_set))
print("new set:", new_set, "new set id:", id(new_set))


# 输出结果
Old set: {1, 2, 3, 4} old set id: 4381115552
new set: {1, 2, 3} new set id: 4381115776

字www.cppcns.com典

from copy import copy

old_dict = {"name": "小明"}
new_xYnPGYHxGNdict = copy(old_dict)

old_dict["second"] = "Python"

print("Old dict:", old_dict, "old dict id:", id(old_dict))
print("new dict:", new_dict, "new dict id:", id(new_dict))


# 输出结果
Old dict: {'name': '小明', 'second': 'Python'} old dict id: 4381159680
new dict: {'name': '小明'} new dict id: 4379632576

到此这篇关于Python中浅拷贝的四种实现方法小结的文章就介绍到这了,更多相关Python 浅拷贝内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！