数据类型-元组&字典

一、元组：tuple

作用：存多个值，对比列表来说，元组不可变（是可以当做字典的key的），主要是用来读取，不可以修改。

#定义：与列表类型对比，只不过[]换成()。即中括号换成小括号

info_of_sean = ('sean',18,'70kg','175cm')
print(type(info_of_sean)) #tuple

info_of_sean = ['sean',18,'70kg','175cm']
print(type(info_of_sean)) # list

二、tuple 优先掌握的操作应用

2.1按索引取值(正向取+反向取)：只能取

print(info_of_sean[0][2]) #返回：a
print(info_of_sean[-1]) #返回：175cm

2.2切片(顾头不顾尾，步长)（开始，终止，步长）

res = info_of_sean[0:2:1]
print(res) #sean 18
info_of_sean[1]=25  #报错，元组不支持改变

2.3长度Len

info_of_sean = ('sean',18,'70kg','175cm')
print(len(info_of_sean)) # 4

2.4成员运算in和not in

msg = 'sean' in info_of_sean
print(msg)

msg = 'sean' not in info_of_sean
print(msg)

2.5循环

for i in info_of_sean:
    print(i) #返回：sean 18 70kg 175cm

三、字典dic

作用：存多个值,key-value存取，取值速度快
定义：key必须是不可变类型，value可以是任意类型
info={'name':'egon','age':18,'sex':'male'} #本质info=dict({....})
或
info=dict(name='egon',age=18,sex='male')
或
info=dict([['name','egon'],('age',18)])
或
{}.fromkeys(('name','age','sex'),None)

四、字典优先掌握的操作应用

info_of_sean = {'name':'sean','age':18,'weight':'70kg','height':'175cm'}

print(type(info_of_sean))  #dict

4.1按key存取值：可存可取

print(info_of_sean['name']) #按key取值
info_of_sean['name']='egon' #按key修改
print(info_of_sean) #返回：{'name': 'egon', 'age': 18, 'weight': '70kg', 'height': '175cm'}

*key不存在则加元素，存在则改值*
info_of_sean['gender'] = 'male'
print(info_of_sean) #{'name': 'sean', 'age': 18, 'weight': '70kg', 'height': '175cm', 'gender': 'male'}

*取值使用get（key）字典中使用*

dic = info_of_sean.get('name')
print(dic)

4.2长度len

info_of_sean = {'name':'sean','age':18,'weight':'70kg','height':'175cm'}
print(len(info_of_sean)) #返回 4

4.3成员运算in和not in

res = 'name' in info_of_sean #key作为判断in或not in的依据
print(res) # TRUE

4.4删除

del info_of_sean['name'] #万能删除，按key删除
print(info_of_sean) #{'age': 18, 'weight': '70kg', 'height': '175cm'}

info_of_sean.pop('age') #pop指定key删除
print(info_of_sean) #{'weight': '70kg', 'height': '175cm'}

4.5对于Dict，索引找不到的，则会默认在末尾增加。如需增加也可以通过setdefault增加，setdefault(key,value)

dic={'age':18}
res = dic.setdefault('name',"SEAN")
print(dic) #{'age': 18, 'name': 'SEAN'}
print(res) #SEAN
sean=dic.setdefault('gentle','male')
print(sean) #male
print(dic) #{'age': 18, 'name': 'SEAN', 'gentle': 'male'}

4.6循环

for i in info_of_sean:
    print(i) #返回key

dic = {'name':'sean','age':18,'gentle':'male'}
for k in dic.keys():
    print(k)

dic = {'name':'sean','age':18,'gentle':'male'}
print(list(dic.keys()))

dic = {'name':'sean','age':18,'gentle':'male'}
for v in dic.values():
    print(v) #返回value值

dic = {'name':'sean','age':18,'gentle':'male'}

for k,v in dic.items():
    print(k,v) #返回key value