基础补充练习

基础补充1——collections模块

命名元组另一个用途就是作为字典的替代,因为字典存储需要更多的内存空间。如果你需要构建一个非常大的包含字典的数据结构,那么使用命名元组会更加高效。但 是需要注意的是,不像字典那样,一个命名元组是不可更改的。

from collections import namedtuple

records=[

    ('mac',2,20000),

    ('lenovo',1,3000),

    ('apple',0,10),

    ('tesla',10,10000000)

]

cost=0.0

for re in records:

    cost+=re[1]*re[2]

    print('商品:%s 购买个数:%s 总价:%s'%(re[0],re[2],cost))

sk=namedtuple('Stock',['name','count','price'])

for re in records:

    s=sk(*re)

    print(s.count,s.price)

p=namedtuple('People',['name','gender','age'])

l=['5537','female',18]

p1=p(*l)

print(p1)

print(p1.name)

print(p1.gender)

print(p1.age)

#p1.name='karla'#报错，不可修改

p1=p1._replace(name='karla')#需要重新赋值给p1

print(p1.name)

#重新设置一个函数，弥补只能使用_replace修改的缺点

p=namedtuple('People',['name','gender','age'])

p1=p('','',None)

def dic_to_stock(s):

    return p1._replace(**s)

print(dic_to_stock({'name':'karla','gender':'female','age':18}))

print(dic_to_stock({'name':'lily','gender':'male','age':30}))

基础补充2——从字典中提取子集

prices={

    'ss':48.78,

    'gg':47.5,

    'll':55.3,

    'zz':66

}

prices_new={key:val for key,val in prices.items() if val>50}

print(prices_new)

基础补充4——带参数的装饰器

 1 name='karla'
 2 pwd='root'
 3 
 4 def auth(auth_type):
 5     def inner_auth(func):
 6         def wrapper(*args,**kwargs):
 7             username=input('username:').strip()
 8             password=input('password:').strip()
 9             if auth_type=='local':
10                 if username==name and password==pwd:
11                     print('user login successful')
12                     return func(*args,**kwargs)
13                 else:
14                     exit('log err')
15             elif auth_type=='ldap':
16                 print('ladp是啥呀')
17         return wrapper
18     return inner_auth
19 
20 def index():
21     print('welcome to index page')
22 
23 @auth(auth_type='local')
24 def home():
25     print('welcome to home page')
26 
27 @auth(auth_type='ladp')
28 def bbs():
29     print('welcome to bbs page')
30 
31 index()
32 home()
33 bbs()

基础补充5——生成器并行运算

import time

def consumer(name):
    print('[%s]准备吃包子啦'%name)
    while True:
        baozi=yield
        print('包子[%s]来啦,被[%s]吃啦 '%(baozi,name))

def producter():
    c1=consumer('Karla')
    c2=consumer('Cindy')
    c1.__next__()
    c2.__next__()
    print('开始做包子啦')
    for i in range(10):
        time.sleep(1)
        c1.send(i)
        c2.send(i)

producter()

f=open('xx.log')
f.__next__()