DAY02

字典

定义: D={}. 逗号分隔元素, 元素为key:value对.

info={'name':'PatHoo','age':18,'sex':'male'}
#本质 info=dict({'name':'PatHoo','age':18,'sex':'male'})

info={'name':'PatHoo','age':18,'sex':'male'}
print(info['age'])
>>> 18
info['height']=1.80
print(info)
>>> {'name': 'PatHoo', 'age': 18, 'sex': 'male', 'height': 1.8}

for key in info:
    print(key)
>>> name
    age
    sex
    height

#字典的key必须是不可变类型，也称为可hash类型

info={(1,2):'a'}
print(info[(1,2)])
>>> a

#字典常用的方法(优先掌握)

info={'name':'PatHoo','age':18,'sex':'male'}
print(info.pop('name'))
>>> PatHoo
print(info)
>>> {'age': 18, 'sex': 'male'}

print(info.pop('asdfsadfasdfasfasdfasdfasdf',None)) #不存在的键值可以指定报错信息, 默认KeyError
>>> None

print(info['name1']) #不存在的键值报错
>>> #KeyError
print(info.get('name1')) #不存在的键值默认返回None
>>> None
print(info.get('nameasdfasdfasdfasdf','not key')) #可以修改默认返回值
>>> not key

#字典其他的方法

info={'name':'PatHoo','age':18,'sex':'male'}
print(info.popitem()) #返回(Key, Value)元组
>>> ('sex','male')
print(info.popitem()) #字典是无序的
>>> ('name','PatHoo')
print(info)
>>> {'age':18}

print(info.keys(),type(info.keys()))
>>> dict_keys(['age']) <class 'dict_keys'>

print(info.values())
>>> dict_values([18])

for key in info.keys():
    print(key)
>>> age

for val in info.values():
    print(val)
>>> 18

for key in info:
    print(key,info[key])
>>> age 18

print(info.items())
>>> dict_items([('age', 18)])

for key,value in info.items(): # key,value=('age',18)
    print(key,value)
>>> age 18

msg_dic={
'apple':10,
'tesla':100000,
'mac':3000,
'lenovo':30000,
'chicken':10,
}
for key,value in msg_dic.items():
    print(key,value)
>>>

      apple 10
      tesla 100000
      mac 3000
      lenovo 30000
      chicken 10

info={'name':'PatHoo','age':18,'sex':'male'}
info.clear()
print(info)
>>> {}

print(info.items())
>>> dict_items([])

dic=info.fromkeys(['name','age','sex'],11111111)
print(dic)
>>> {'name': 11111111, 'age': 11111111, 'sex': 11111111}

dic=info.fromkeys(['name','age','sex'],None)
print(dic)
>>> {'name': None, 'age': None, 'sex': None}

dic=dict(a=1,b=2,c=3)
print(dic)
>>> {'a': 1, 'b': 2, 'c': 3}

print(dict([('name', 'PatHoo'), ('age', 18), ('sex', 'male')]))
>>> {'name': 'PatHoo', 'age': 18, 'sex': 'male'}

print(info)
>>> {}
dic={'a':1,'b':2,'name':'SHUAI'}
info.update(dic)
print(info)
>>> {'a': 1, 'b': 2, 'name': 'SHUAI'}

d={}
d['name']='PatHoo'
d['age']=18
d['sex']='male'
d['hobby']=[]
d['hobby'].append('play basketball')
d['hobby'].append('play football')
print(d)
>>> {'name': 'PatHoo', 'age': 18, 'sex': 'male', 'hobby': ['play basketball', 'play football']}

d.setdefault('hobby',[]).append('play1') #d['hobby']
d.setdefault('hobby',[]).append('play2') #d['hobby']
d.setdefault('hobby',[]).append('play3') #d['hobby']
print(d)
>>> {'name': 'PatHoo', 'age': 18, 'sex': 'male', 'hobby': ['play basketball', 'play football', 'play1', 'play2', 'play3']}