Python字典基础知识

D={}#创建一个空字典

D['name']='李明'#给字典添加键值对
D['age']=18

D['name']='李刚'#修改值
print(D.items())

del D['name']#删除键值对

favoritefood={   #由类似对象组成的字典，储存多个对象的同一个信息
	'jack':'milk',
	'bob':'pork',
	'cindy':'beef',
	}

food1=favoritefood.get('jack','there is no this person')#通过get方法来访问值，第二个参数是键不存在的情况

S={'a':'1','b':'2','c':'3'}
for k,v in S.items():#遍历所有键值对
	print(k.title()+' is '+v)
for k in S.keys():#遍历所有键，keys方法返回可以得到一个列表
	print(k,end=' ')
	
R=['b','c','d']
for i in S.keys():#列表和遍历键的结合
    if i in R:
        print('\n'+i+' is '+S[i],end=' ')
print('\n')
for i in sorted(S.keys()):#按特定顺序遍历，用sorted等
	print(i,end=" ")

for i in S.values():#遍历所有值
	print(i,end=' ')
print('\n')
S1=set(S)#集合去重
print(S1)

a={'1':'a'}
b={'2':'b'}
c={'3':'c'}
ls=[a,b,c]#在列表中镶嵌字典，即字典列表

fl={                     #在列表中存储字典
    'jack':['python','c'],
    'shy':['python'],
    'davis':['r','java'],
    }

for name,languages in sorted(fl.items()):#列表字典的实例
    if len(languages)==1:
        print(f"\n{name.title()}'s favorite language is:\n\t{languages[0].title()}")
    else:
        print(f"\n{name.title()}'s favorite languages are:")
        for language in languages:
            print(f"\t{language.title()}")

users={        #字典嵌套实例
	'汧然':{
		'name':'李明',
		'age':'18'
	},
	'子归':{
		'name':'赵刚',
		'age':'14'
	}
}
for user,info in users.items():
	print(f"\nUsername:{user}")
	print(f"用户的真名是{info['name']},用户的年龄是{info['age']}")

dict_items([('name', '李刚'), ('age', 18)])
A is 1
B is 2
C is 3
a b c 
b is 2 
c is 3 

a b c 1 2 3 

{'b', 'c', 'a'}

Davis's favorite languages are:
	R
	Java

Jack's favorite languages are:
	Python
	C

Shy's favorite language is:
	Python

Username:汧然
用户的真名是李明,用户的年龄是18

Username:子归
用户的真名是赵刚,用户的年龄是14
>>>