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