字典
增改删查
a={'name':'小红','age':'25','address':'北京'}
print(a['name']) #查找键值对
a['sex']='女' #增加键值对
print(a)
a['age']='18' #修改键值对
print(a)
del a['sex'] #删除键值对
print(a)
a.pop('name') #删除键值对,但返回删除的值,print(a.pop('name'))输出为name
print(a)
a.clear() #清空字典
print(a)
pop默认弹出最后一个
a={'name':'小红','age':'25','address':'北京'}
print(a.popitem())
print(a)
dict():
a=dict(name='张三',age='23',address='北京')
print(a)
print(a['sex']) #报错,KeyError
范围
a=[1,2]
print(a[0],a[1])
print(a[2]) #超出范围,报错
a.get用法:
a=dict(name='张三',age='23',address='北京')
print(a.get('name'))
print(a.get('sex')) #没有key,输出None
print(a.get('sex','男')) #没有的key值,a,get添加的值为默认值进行输出
print(a.get('name','李四')) #有key值,输出原值,不改变
print(a)
输出示例:
一些操作==
a=dict(name='张三',age='23',address='北京')
print(a)
print(a.keys()) #输出所有key
输出键,值,键值对
a=dict(name='张三',age='23',address='北京')
for key in a.keys():
print(key) #输出键
print(key,a[key]) #输出键值对
for v in a.values():
print(v) #输出值
字典用元组表示出来并进行输出:
a={'name':'小红','age':'25','address':'北京'}
print(a.items()) #每组用元组表示出来
for k,v in a.items():
print(k,v)
for item in a.items():
k,v=item
print(k,v)
输出示例:
例题:
展开字典中的字典,去掉‘:’
a={
'001':{'name':'lilei','age':'23','address':'China'},
'002':{'name':'zhang','age':'43','address':'American'},
'003':{'name':'lishi','age':'67','address':'England'},
}
for i in a.keys():
print(i,end=' ')
for k in a[i].keys():
print(k,a[i][k],end=' ')
print()
items写法:
for k,v in a.items():
print(k,end=' ')
for k1,v1 in v.items():
print(k1,v1,end=' ')
print()
输出示例:
将地址为China的序号加上‘house’=10000
a={
'001':{'name':'lilei','age':'23','address':'China'},
'002':{'name':'zhang','age':'43','address':'American'},
'003':{'name':'lishi','age':'67','address':'England'},
'004':{'name':'liliu','age':'27','address':'China'},
'005':{'name':'ming1','age':'61','address':'England'},
}
for i in a.keys():
if a[i]['address']=='China':
a[i]['house']=10000
#print(a)
for k,v in a.items():
print(k,v)
输出示例: