生成器

生成器总结

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 8:58
 3 # @Author:Henry Scofield
 4 # @File:2.py
 5 # @Software:PyCharm
 6 
 7 age = 10
 8 res = True if age > 10 else False
 9 List = ['a' for i in range(10)]
10 g_List = ('a' for i in range(10))  # 生成器表达式
11 
12 
13 def test():
14     for i in range(4):
15         yield i
16 
17 
18 t = test() # t生成器对象
19 
20 for i in t:  # 如果这里遍历完了，下面list(t1)就是空列表了！
21     print(i)
22 
23 # print(t) # 
24 t1 = (i for i in t)  # t1 生成器对象
25 # print(t1) #  at 0x0000019A4A229A50>
26 print(list(t1))  # [0, 1, 2, 3]

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 8:58
 3 # @Author:Henry Scofield
 4 # @File:2.py
 5 # @Software:PyCharm
 6 
 7 age = 10
 8 res = True if age > 10 else False
 9 List = ['a' for i in range(10)]
10 g_List = ('a' for i in range(10))  # 生成器表达式
11 
12 
13 def test():
14     for i in range(4):
15         yield i
16 
17 
18 t = test()  # t生成器对象，要迭代才有值，迭代完就没值了
19 
20 t1 = (i for i in t)
21 t2 = (i for i in t)
22 print(list(t1))  # [0, 1, 2, 3] # 如果这里遍历完了，下面list(t1)就是空列表了！
23 print(list(t2))  # []

迭代器协议

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 8:39
 3 # @Author:Henry Scofield
 4 # @File:def函数.py
 5 # @Software:PyCharm
 6 def test():
 7     yield 1  # 相当于return 1
 8     yield 2
 9     # print("")
10 
11 
12 t = test()
13 
14 
15 def run():
16     print("from run")
17     print("from run")
18     print("from run")
19 
20 
21 run()
22 
23 
24 def test():
25     print("from run")
26     yield 1  # 相当于return 相当于保存状态，next()一次用一次
27     print("from run")
28     yield 2
29     # print("")
30 
31 
32 t = test()
33 
34 # 迭代器协议 可迭代对象
35 next(t)
36 
37 print("abcd")
38 print("abcd")
39 print("abcd")
40 print("abcd")
41 
42 next(t)
43 
44 # t.__next__() 从上次迭代后的位置开始迭代。 # StopIteration 已经走完了两个print,在迭代会报错
45 # t.send('123')# StopIteration 已经走完了两个print,在迭代会报错

装饰器

迭代器：

装饰器：本质就是函数，功能：为其他函数添加附加功能。

原则：

1.不修改被修饰函数的源代码；

2.不修改被修饰函数的调用方式。

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 9:21
 3 # @Author:Henry Scofield
 4 # @File:3.py
 5 # @Software:PyCharm
 6 import time
 7 
 8 
 9 # 被修饰函数上线后，不能随意再改源代码
10 def cal(l):
11     start_time = time.time()
12     res = 0  # 初始为0
13     for i in l:
14         time.sleep(0.1)
15         res += i  # 求和
16     stop_time = time.time()
17     print("函数的运行时间是 %s " % (stop_time - start_time))
18     return res
19 
20 
21 print(cal(range(100)))
22 
23 
24 def index():
25     pass
26 
27 
28 def home():
29     pass
30 
31 
32 index()  # index()调用就index()调用，不修改被修饰函数的调用方式

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 9:31
 3 # @Author:Henry Scofield
 4 # @File:4.py
 5 # @Software:PyCharm
 6 import time
 7 
 8 
 9 def timmer(func):
10     def wapper(*args, **kwargs):
11         start_time = time.time()
12         res = func(*args, **kwargs)
13         stop_time = time.time()
14         print("函数的运行时间是 %s " % (stop_time - start_time))
15         return res
16 
17     return wapper
18 
19 
20 @timmer
21 def cal(l):
22     res = 0  # 初始为0
23     for i in l:
24         time.sleep(0.1)
25         res += i  # 求和
26     return res
27 
28 
29 res = cal(range(20))
30 print(res)

装饰器的知识储备

装饰器 = 高阶函数 + 函数嵌套 + 闭包

 高阶函数

 1 # -*- coding:utf-8 -*-
 2 # @Time:2022/4/1 9:40
 3 # @Author:Henry Scofield
 4 # @File:5-高阶函数.py
 5 # @Software:PyCharm
 6 import time
 7 
 8 # def foo():
 9 #     time.sleep(3)
10 #     print("Hello!")
11 #
12 #
13 # def test(func):
14 #     print(func)
15 #     start_time = time.time()
16 #     func()  # 输出参数的值
17 #     stop_time = time.time()
18 #     print("函数运行时间是 %s " % (stop_time - start_time))
19 #
20 #
21 # test(foo)
22 # # 输出，函数接收的参数是一个函数名
23 # # Hello!
24 
25 # def foo():
26 #     print("from the foo")
27 #
28 #
29 # def test(func):
30 #     return func
31 #
32 #
33 # res = test(foo)
34 # # print(res) # 
35 # # res() # from the foo
36 
37 # 多运行了一步
38 import time
39 
40 
41 def foo():
42     time.sleep(3)
43     print("来自foo")
44 
45 
46 # 添加统计运行时间功能
47 # 不修改foo 源代码
48 # 不修改foo 调用方式
49 def timer(func):
50     start_time = time.time()
51     func() # 来自foo
52     stop_time = time.time()
53     print("函数的运行时间是 %s " % (stop_time - start_time))
54     return func
55 
56 
57 foo = timer(foo)
58 foo() # 来自foo