day14,函数的使用方法：生成器表达式，生成器函数

生成器表达式：

#列表推导式
# y = [1,2,3,4,5,6,7,8]
# x = [1,4,9,16,25,36,49,64]
# x = []
# for i in y:
#     x.append(i*i)
# print(x)
# x = [i*i for i in y]
# print(x)

#range(100)
# x2 = [i/2 for i in range(100)]
# print(x2)

#生成器表达式

# x = [i*i for i in y]
# print(x)
# g = (i*i for i in y)
# print(g)
# print(list(g))
# for i in g:
#     print(i)

#
# l = ['鸡蛋%s'%i for i in range(10)]
# print(l)
# laomuji = ('鸡蛋%s'%i for i in range(10))
# for egg in laomuji:
#     print(egg)

生成器函数：

 # def cloth():
 #     for i in range(100):
 #         yield  '衣服%s'%i
 #
 # g = cloth()
 # for i in g:
 #     print(i)

 # for i in range(100):
 #     print(g.__next__())
 #
 # for i in range(50):
 #     print(g.__next__())

 #监听文件末尾追加的例子
 # def tail():
 #     f = open('文件','r',encoding='utf-8')
 #     f.seek(0,2)
 #     while True:
 #         line = f.readline()
 #         if line:
 #             yield line
 #         import time
 #         time.sleep(0.1)
 # g = tail()
 # for i in g:
 #     print(i.strip())

 # send
 def func():
     print('*'*10)
     a = yield 5
     print('a : ',a)
     yield 10
 # g = func()
 # num = g.__next__()
 # # print(num)
 # num2 = g.send('alex')
 # num2 = g.send('aaaa')
 # print(num2)

 #从哪一个yield开始接着执行，就把一个值传给了那个yield
 #send不能用在第一个触发生成器
 #生成器函数中有多少个yield就必须有多少个next+send

 def averager():
     total = 0.0
     count = 0
     average = None
     while True:
         term = yield average
         total += term
         count += 1
         average = total/count
 #
 # g_avg = averager()
 # g_avg.__next__()
 # print(g_avg.send(10))
 # print(g_avg.send(30))
 # print(g_avg.send(20))
 # print(g_avg.send(100))
 # print(g_avg.send(200))
 def init(func):  #生成器的预激装饰器
     def inner(*args,**kwargs):
         g = func(*args,**kwargs)   #func = averager
         g.__next__()
         return g
     return inner

 @init
 def averager():
     total = 0.0
     count = 0
     average = None
     term = yield average
     total += term
     count += 1
     average = total/count
     yield average

 # g_avg = averager()
 # print(g_avg.send(10))
 # print(g_avg.send(30))

 #生成器函数 讲完了
     #next
     #进阶 send

 #网络编程 ： ftp
 def func():
     a = 'AB'
     b = 'CD'
     yield from a
     # for i in a:yield i
     yield from b
     # for i in b:yield i

 'A','B','C','D'
 #返回了4次
 g = func()
 # for i in g:
 #     print(i)

 #生成器函数：生成一个生成器的函数
 #生成器的本质参数迭代器
 #生成器函数的特点：
 # 带有yield关键字
 # 且调用之后，函数内的代码不执行

 #触发执行的方式：
     #next
     #send (选会) ：send(None) == __next__(),send在next的基础上传一个值到生成器函数内部
                   #send操作不能用在生成器使用的第一次
     #for循环

 def cloth():
     for i in range(100):
         yield '衣服%s'%i

 g1 = cloth()
 g2 = cloth()
 print(g.__next__())
 print(g.__next__())
 # for c in cloth():
 #     print(c)
 # print(g.__next__())
 # for i in range(10):
 #     print(g.__next__())
 # for i in range(100):
 #     print(g.__next__())
 # for c in g:
 #     print(c)
 #     if c.endswith('80'):
 #         break
 # print(g.__next__())
 # print('*'*20)
 # for c in g:
 #     print(c)

 # g.__next__() #== next(g)
 # g.__iter__() #== iter(g)
 #内置函数

推导式拓展：

# new_l = []
# for i in range(30):
#     if i%3 == 0:
#         new_l.append(i)
# print(new_l)
#
# print(list(range(0,30,3)))
# print([i for i in range(30) if i%3 == 0])
# [i*i for i in range(30) if i%3 == 0]
# def square(x):
#     return x*x
# [square(i) for i in range(30) if i%3 == 0]

# names = [['Tom', 'Billy', 'Jefferson', 'Andrew', 'Wesley', 'Steven', 'Joe'],
#          ['Alice', 'Jill', 'Ana', 'Wendy', 'Jennifer', 'Sherry', 'Eva']]
# ret = (name for name_lst in names for name in name_lst if name.count('e') >= 2)
# print(ret)
# 不利于代码可读，但是代码简洁

# mcase = {'a': 10, 'b': 34}
# mcase_frequency = {mcase[k]:k for k in mcase}
# print(mcase_frequency)

# mcase = {'a': 10, 'b': 34, 'A': 7, 'Z': 3}
# mcase_frequency = {k.lower(): mcase.get(k.lower(), 0) + mcase.get(k.upper(), 0) for k in mcase}
# print(mcase_frequency)

squared = {x**2 for x in [1, -1, 2]}   #{1,4}
print(squared)
# Output: set([1, 4])

#考试
#2:00 --> 敲敲代码
#明天 ：
# 装饰器剩余的两个例子
# 今天的考试内容明天要讲
#明天的默写：
#[i/2 for i in range(100)]
#[i*i for i in range(30) if i % 3 is 0]
# 修改成生成器表达式，且要求讲使用方法默写出来