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【python】字典超详解

Python 详解 字典
2023-06-13 09:17:21 时间

注：最后有面试挑战，看看自己掌握了吗

文章目录

键值对dict—哈希表构成（无序）

不能直接修改键， 本质是哈希表，键不能重复！ 值可以是python支持的任何对象

增

法1

if '__main__' == __name__:
    d={1:123,2:569}
    d[3] = 123
    print(d)

法2

setdefault函数，默认为None

if '__main__' == __name__:
    d={1:123,2:569}
    d.setdefault(3,'129z')
    print(d)

查

法1

	d={1:123,2:569}
    d.setdefault(3,'129z')
    print(d[2])

法2

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    d.setdefault('zzz', '129z')
    print(d.get('zzz'))

改

法1

法2-也可用来新增

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    d.setdefault('zzz', '129z')
    d.update({'zzz':'111'})
    print(d.get('zzz'))

删

法1

del函数

from Box_model import *
import math
import sys

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    d.setdefault('zzz', '129z')
    d.update({'zzz':'111'})
    print(d.get('zzz'))
    del(d[1])
    print(d)

法2

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    p = d.pop(1)
    print(p)

法3

随机返回一个键值对元组，并且删除对应元素

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    p = d.popitem()
    print(p)
if '__main__' == __name__:
    d = {1: 123, 2: 569}
    k,v = d.popitem()
    print(v)

遍历

遍历所有键值对

item()–以元组返回所有字典元素

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    for item in d.items():
        print(item)
if '__main__' == __name__:
    d = {1: 123, 2: 569}
    print(d.items())//<class 'builtin_function_or_method'>

遍历所有键

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    for i in d:
        print(i)
if '__main__' == __name__:
    d = {1: 123, 2: 569}
    for i in d.keys():
        print(i)

遍历所有值

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    for i in d.values():
        print(i)
if '__main__' == __name__:
    d = {1: 123, 2: 569}
    for i in d:
        print(d[i])

其他方法

in

if ‘item’ in d

clear

copy

if '__main__' == __name__:
    d = {1: 123, 2: 569}
    d2 = d.copy()
    print(id(d))
    print(id(d2))
2757616058112
2757616058304
if '__main__' == __name__:
    d = {1: 123, 2: 569}
    d2 = d
    print(id(d))
    print(id(d2))
2818139340544
2818139340544

fromkeys-指定相关键 生成 空值字典

if '__main__' == __name__:
    d = {}.fromkeys('1','zzz')
    print(d)

{'1': 'zzz'}

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