12、闭包函数、装饰器、迭代器

'''
一、闭包:
1. 定义在内部函数
2. 包含对外部作用域而非全局作用域的引用,
该内部函数就成为闭包函数
'''
#
# def f1():
#     x = 1
#     def f2():
#         print(x)
#
#     return f2
#
# f=f1()
# # print(f)
#
# x=100000000000000000000000000
# f()




#闭包应用：惰性计算

from urllib.request import urlopen

def index(url):
    def get():
        return urlopen(url).read()

    return get

oldboy=index('http://crm.oldboyedu.com')

# print(oldboy().decode('utf-8'))
# print(oldboy.__closure__[0].cell_contents)


# res=urlopen('http://crm.oldboyedu.com').read()
#
# print(res.decode('utf-8'))




x=1
# y=2
def f1():
    # x=1
    y=2
    def f2():
        print(x,y)
    return f2

f=f1()
print(f.__closure__[0].cell_contents)

二、装饰器

'''
装饰器：修饰别人的工具，修饰添加功能，工具指的是函数

装饰器本身可以是任何可调用对象，被装饰的对象也可以是任意可调用对象


为什么要用装饰器：
    开放封闭原则：对修改是封闭的，对扩展是开放的
    装饰器就是为了在不修改被装饰对象的源代码以及调用方式的前提下，为期添加新功能

'''




import time

def timmer(func):
    def wrapper(*args,**kwargs):
        start_time=time.time()
        res=func(*args,**kwargs)
        stop_time=time.time()
        print('run time is %s' %(stop_time-start_time))
    return wrapper

@timmer
def index():

    time.sleep(3)
    print('welcome to index')

index()



# import time
#
# def timmer(func):
#     def wrapper():
#         start_time=time.time()
#         func() #index()
#         stop_time=time.time()
#         print('run time is %s' %(stop_time-start_time))
#     return wrapper
#
#
# @timmer #index=timmer(index)
# def index():
#     time.sleep(3)
#     print('welcome to index')
#
#
# # f=timmer(index)
# # # print(f)
# # f() #wrapper()---->index()
#
# # index=timmer(index) #index==wrapper
#
# index() #wrapper()----->



#流程分析
# import time
# def timmer(func):
#     def wrapper():
#         start_time=time.time()
#         func()
#         stop_time=time.time()
#         print('run time is %s' %(stop_time-start_time))
#     return wrapper
#
# @timmer #index=timmer(index)
# def index():
#     time.sleep(3)
#     print('welcome to index')
#
#
# index() #wrapper()








# import time
# def timmer(func):
#     def wrapper(*args,**kwargs):
#         start_time=time.time()
#         res=func(*args,**kwargs)
#         stop_time=time.time()
#         print('run time is %s' %(stop_time-start_time))
#         return res
#     return wrapper
#
# @timmer #index=timmer(index)
# def index():
#     time.sleep(3)
#     print('welcome to index')
#     return 1
#
# @timmer
# def foo(name):
#     time.sleep(1)
#     print('from foo')
#
#
# res=index() #wrapper()
# print(res)
#
# res1=foo('egon')  #res1=wrapper('egon')
# print(res1)
#
#

# def auth(func):
#     def wrapper(*args,**kwargs):
#         name=input('>>: ')
#         password=input('>>: ')
#         if name == 'egon' and password == '123':
#             print('33[45mlogin successful33[0m')
#             res=func(*args,**kwargs)
#             return res
#         else:
#             print('33[45mlogin err33[0m')
#     return wrapper
#
#
#
# @auth
# def index():
#     print('welcome to index page')
# @auth
# def home(name):
#     print('%s welcome to home page' %name)
#
# index()
# home('egon')
#


# login_user={'user':None,'status':False}
# def auth(func):
#     def wrapper(*args,**kwargs):
#         if login_user['user'] and login_user['status']:
#             res=func(*args,**kwargs)
#             return res
#         else:
#             name=input('>>: ')
#             password=input('>>: ')
#             if name == 'egon' and password == '123':
#                 login_user['user']='egon'
#                 login_user['status']=True
#                 print('33[45mlogin successful33[0m')
#                 res=func(*args,**kwargs)
#                 return res
#             else:
#                 print('33[45mlogin err33[0m')
#     return wrapper
#
# @auth
# def index():
#     print('welcome to index page')
# @auth
# def home(name):
#     print('%s welcome to home page' %name)
# index()
# home('egon')

三、迭代器
'''
迭代器
迭代的概念:重复+上一次迭代的结果为下一次迭代的初始值
重复的过程称为迭代,每次重复即一次迭代，
并且每次迭代的结果是下一次迭代的初始值

'''


# while True: #只满足重复，因而不是迭代
#     print('====>')


#下面才为迭代
# l = [1, 2, 3]
# count = 0
# while count < len(l):  # 只满足重复，因而不是迭代
#     print('====>', l[count])
#     count += 1
#
# l = (1, 2, 3)
# count = 0
# while count < len(l):  # 只满足重复，因而不是迭代
#     print('====>', l[count])
#     count += 1

# s='hello'
# count = 0
# while count < len(s):
#     print('====>', s[count])
#     count += 1
#


#为什么要有迭代器？对于没有索引的数据类型，必须提供一种不依赖索引的迭代方式

#可迭代的对象:内置__iter__方法的，都是可迭代的对象

# [1,2].__iter__()
# 'hello'.__iter__()
# (1,2).__iter__()
#
# {'a':1,'b':2}.__iter__()
# {1,2,3}.__iter__()

#迭代器：执行__iter__方法，得到的结果就是迭代器，迭代器对象有__next__方法
# i=[1,2,3].__iter__()
#
# print(i)
#
# print(i.__next__())
# print(i.__next__())
# print(i.__next__())
# print(i.__next__()) #抛出异常：StopIteration


# i={'a':1,'b':2,'c':3}.__iter__()

# print(i.__next__())
# print(i.__next__())
# print(i.__next__())
# print(i.__next__())

# dic={'a':1,'b':2,'c':3}
# i=dic.__iter__()
# while True:
#     try:
#         key=i.__next__()
#         print(dic[key])
#     except StopIteration:
#         break



# s='hello'
# print(s.__len__())
#
# print(len(s))
#
# len(s)====== s.__len__()


s={'a',3,2,4}

# s.__iter__() #iter(s)

# i=iter(s)
# print(next(i))
# print(next(i))
# print(next(i))
# print(next(i))
# print(next(i))


#如何判断一个对象是可迭代的对象，还是迭代器对象
from collections import Iterable,Iterator

# 'abc'.__iter__()
# ().__iter__()
# [].__iter__()
# {'a':1}.__iter__()
# {1,2}.__iter__()

# f=open('a.txt','w')
# f.__iter__()


#下列数据类型都是可迭代的对象
# print(isinstance('abc',Iterable))
# print(isinstance([],Iterable))
# print(isinstance((),Iterable))
# print(isinstance({'a':1},Iterable))
# print(isinstance({1,2},Iterable))
# print(isinstance(f,Iterable))



#只有文件是迭代器对象
# print(isinstance('abc',Iterator))
# print(isinstance([],Iterator))
# print(isinstance((),Iterator))
# print(isinstance({'a':1},Iterator))
# print(isinstance({1,2},Iterator))
# print(isinstance(f,Iterator))



'''
可迭代对象：只有__iter__方法，执行该方法得到的迭代器对象

迭代协议：
    对象有__next__
    对象有__iter__,对于迭代器对象来说，执行__iter__方法，得到的结果仍然是它本身


'''
# f1=f.__iter__()
#
# print(f)
# print(f1)
# print(f is f1)

#
# l=[]
# i=l.__iter__()
#
# print(i.__iter__())
# print(i)
# print(l)


dic={'name':'egon','age':18,'height':'180'}
# print(dic.items())

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

# i=iter(dic)
# while True:
#     try:
#         k=next(i)
#         print(k)
#     except StopIteration:
#         break
# for k in dic: #i=iter(dic)  k=next(i)
#     print(k)
#     print(dic[k])
#



# l=['a','b',3,9,10]
# for i in l:
#     print(i)



# with open('a.txt','r',encoding='utf-8') as f:
#     for line in f:
#         print(line)
    # print(next(f))
    # print(next(f))
    # print(next(f))
    # print(next(f))
    # print(next(f))
    # print(next(f))
    # print(next(f))
    # print(next(f))


'''
迭代器的优点和缺点
优点：
    1.提供了一种不依赖下标的迭代方式
    2.就跌迭代器本身来说，更节省内存

缺点：
    1. 无法获取迭代器对象的长度
    2. 不如序列类型取值灵活，是一次性的，只能往后取值，不能往前退
'''
# l=[10000,2,3,4,5]
#
# i=iter(l)
#
# print(i)
# print(next(i))
#
# f=open('a.txt',encoding='utf-8')
#
# for line in f.readlines():
#     print(line)

# print(next(f))

# for line in f:
#     print(line)




# l=[10000,2,3,4,5]
#
# i=iter(l)
#
# for item in i:
#     print(item)
# print('=============================')
#
#
# for item in i:
#     print(item)

l=[10000,2,3,4,5]

i=enumerate(l)

print(next(i))
print(next(i))