0x3 Python学习之路之Python列表copy

墨蓝 2022-05-17 09:37 220阅读 0赞

初认识copy

import copy
    
    names = ["China", "ShanDong", "LiaoCheng", "University"]
    names2 = names.copy()
    print(names)
    print(names2)
    #['China', 'ShanDong', 'LiaoCheng', 'University']
    #['China', 'ShanDong', 'LiaoCheng', 'University']

修改列表信息，认识copy

import copy
    names = ["China", "ShanDong", "LiaoCheng", "University"]
    names2 = names.copy()
    names[2] = "DongChang"
    print(names,names2)
    #['China', 'ShanDong', 'DongChang', 'University'] ['China', 'ShanDong', 'LiaoCheng', 'University']

浅copy

names = ["China", "ShanDong", "LiaoCheng",["GJHe","ymxowgk"] ,"University"]
    names2 = names.copy()
    names[2] = "DongChang"
    print(names)
    print(names2)
    #['China', 'ShanDong', 'DongChang', ['GJHe', 'ymxowgk'], 'University'] ['China', 'ShanDong', 'LiaoCheng', ['GJHe', 'ymxowgk'], 'University']
    #拷贝的内存地址

浅copy的三种方式：

person = ['name',['money',100]]
    p1 = copy.copy(person)
    p2 = person[:]
    p3 = list(person)

浅copy应用
    
    创建联合账号，例如张三和马荣是一对夫妻关系，他俩有个共同银行账户，当张三取钱时，马荣账户跟随改变

person = ['name',['money',100]]
    p1 = person[:]
    p2 = person[:]
    
    p1[0] = "张三"
    p2[0] = "马荣"
    
    p1[1][1] = 50
    
    print(p1)
    print(p2)
    #输出
    #['张三', ['money', 50]]
    #['马荣', ['money', 50]]

字符串，列表赋值更新区别

#字符串
    a = 1;
    b = a;
    a = 2;
    print("a:",a,"b:",b)
    #a: 2 b: 1
    
    
    #列表
    a = [1,2,4]
    b = a
    a[1] = 3333
    print("a:",a,"b:",b)
    #a: [1, 3333, 4] b: [1, 3333, 4]

深copy

names = ["China", "ShanDong", "LiaoCheng",["GJHe","ymxowgk"] ,"University"]
    names2 = copy.deepcopy(names)
    print(names)
    print(names2)
    names[2] = "DongChang"
    names[3][0] = "gaojihe"
    print(names)
    print(names2)
    
    #['China', 'ShanDong', 'LiaoCheng', ['GJHe', 'ymxowgk'], 'University']
    #['China', 'ShanDong', 'LiaoCheng', ['GJHe', 'ymxowgk'], 'University']
    #['China', 'ShanDong', 'DongChang', ['gaojihe', 'ymxowgk'], 'University']
    #['China', 'ShanDong', 'LiaoCheng', ['GJHe', 'ymxowgk'], 'University']

#这样复制就不会改变子列表的值了，是因为deepcopy将子列表也复制了一份
    #注：不过，deepcopy方法，如果数据很大，完全复制就是存储两份数据，占用内存，慎用！

遍历列表元素

names = ["China", "ShanDong", "LiaoCheng", "University"]
    for i in names :
        print(i)
    
    
    #输出
    China
    ShanDong
    LiaoCheng
    University

列表跳着切片

names = ["China", "ShanDong", "LiaoCheng", "University"]
    
    
    print(names[0:-1:2])#[::2]
    
    #['China', 'LiaoCheng']