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)

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生成器函数：

  1 # def cloth():
  2 #     for i in range(100):
  3 #         yield  '衣服%s'%i
  4 #
  5 # g = cloth()
  6 # for i in g:
  7 #     print(i)
  8 
  9 # for i in range(100):
 10 #     print(g.__next__())
 11 #
 12 # for i in range(50):
 13 #     print(g.__next__())
 14 
 15 #监听文件末尾追加的例子
 16 # def tail():
 17 #     f = open('文件','r',encoding='utf-8')
 18 #     f.seek(0,2)
 19 #     while True:
 20 #         line = f.readline()
 21 #         if line:
 22 #             yield line
 23 #         import time
 24 #         time.sleep(0.1)
 25 # g = tail()
 26 # for i in g:
 27 #     print(i.strip())
 28 
 29 # send
 30 def func():
 31     print('*'*10)
 32     a = yield 5
 33     print('a : ',a)
 34     yield 10
 35 # g = func()
 36 # num = g.__next__()
 37 # # print(num)
 38 # num2 = g.send('alex')
 39 # num2 = g.send('aaaa')
 40 # print(num2)
 41 
 42 #从哪一个yield开始接着执行，就把一个值传给了那个yield
 43 #send不能用在第一个触发生成器
 44 #生成器函数中有多少个yield就必须有多少个next+send
 45 
 46 def averager():
 47     total = 0.0
 48     count = 0
 49     average = None
 50     while True:
 51         term = yield average
 52         total += term
 53         count += 1
 54         average = total/count
 55 #
 56 # g_avg = averager()
 57 # g_avg.__next__()
 58 # print(g_avg.send(10))
 59 # print(g_avg.send(30))
 60 # print(g_avg.send(20))
 61 # print(g_avg.send(100))
 62 # print(g_avg.send(200))
 63 def init(func):  #生成器的预激装饰器
 64     def inner(*args,**kwargs):
 65         g = func(*args,**kwargs)   #func = averager
 66         g.__next__()
 67         return g
 68     return inner
 69 
 70 @init
 71 def averager():
 72     total = 0.0
 73     count = 0
 74     average = None
 75     term = yield average
 76     total += term
 77     count += 1
 78     average = total/count
 79     yield average
 80 
 81 # g_avg = averager()
 82 # print(g_avg.send(10))
 83 # print(g_avg.send(30))
 84 
 85 
 86 #生成器函数 讲完了
 87     #next
 88     #进阶 send
 89 
 90 #网络编程 ： ftp
 91 def func():
 92     a = 'AB'
 93     b = 'CD'
 94     yield from a
 95     # for i in a:yield i
 96     yield from b
 97     # for i in b:yield i
 98 
 99 'A','B','C','D'
100 #返回了4次
101 g = func()
102 # for i in g:
103 #     print(i)
104 
105 
106 #生成器函数：生成一个生成器的函数
107 #生成器的本质参数迭代器
108 #生成器函数的特点：
109 # 带有yield关键字
110 # 且调用之后，函数内的代码不执行
111 
112 #触发执行的方式：
113     #next
114     #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
115                   #send操作不能用在生成器使用的第一次
116     #for循环
117 
118 def cloth():
119     for i in range(100):
120         yield '衣服%s'%i
121 
122 g1 = cloth()
123 g2 = cloth()
124 print(g.__next__())
125 print(g.__next__())
126 # for c in cloth():
127 #     print(c)
128 # print(g.__next__())
129 # for i in range(10):
130 #     print(g.__next__())
131 # for i in range(100):
132 #     print(g.__next__())
133 # for c in g:
134 #     print(c)
135 #     if c.endswith('80'):
136 #         break
137 # print(g.__next__())
138 # print('*'*20)
139 # for c in g:
140 #     print(c)
141 
142 
143 # g.__next__() #== next(g)
144 # g.__iter__() #== iter(g)
145 #内置函数

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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

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