迭代器、生成器、裝飾器

迭代器:iter

  迭代器時訪問集合元素的一種方式。

/alex3714/articles/5143440.html

obj_iter.__next__() 只有一個next方法

obj_fileopen.read() 將全部文件讀入

obj_fileopen.readlines()將全部文件按行讀入

 

for line in obj_fileopen:

　　print(line)    #按行讀入，不會將全部文件一次性讀入

 

生成器：generator

一個函數調用時返回一個迭代器，那這個函數就叫生成器，若是函數中包含yield，那這個函數就變成了生成器

 1 >>> def cash_money(amount):
 2 ...     while amount >0:
 3 ...             amount -= 100
 4 ...             yield 100
 5 ...             print("又來取錢了")
 6 ... 
 7 >>> atm = cash_money(300)
 8 >>> atm.__next__()
 9 100
10 >>> atm.__next__()
11 又來取錢了
12 100
13 >>> atm.__next__()
14 又來取錢了
15 100
16 >>> atm.__next__()
17 又來取錢了
18 Traceback (most recent call last):
19   File "<stdin>", line 1, in <module>
20 StopIteration

把函數執行一部分，先中斷，能夠暫時去幹別的，再回來繼續作，即實現異步操做。能夠在while循環中切出切入

 /wupeiqi/articles/4980620.html

 在python中，函數能夠做爲參數，把函數名傳遞給函數做爲形參，亦可return一個函數，將包含一個函數做爲形參的函數返回值賦值給一個變量，那麼這個變量加上（）就開始執行這個返回的函數。例子：

 1 def login(obj_func):
 2     print("This is login page.")
 3     print("You had successed login!")
 4     return obj_func
 5 
 6 def homepage():
 7     print("This is the homepage.")
 8 
 9 def tv():
10     print("This is the TV page.")
11 
12 def shop(name):
13     print("This is the shop page.")
14 
15 
16 tv = login(tv)
17 tv()
18 >>>
19 This is login page.
20 You had successed login!
21 This is the TV page.

帶參數：

 1 def login(obj_func):
 2     print("This is login page.")
 3     print("You had successed login!")
 4     return obj_func
 5 
 6 def homepage():
 7     print("This is the homepage.")
 8 
 9 def tv(name):
10     print("This is the TV page.Hello %s"%name)
11 
12 def shop(name):
13     print("This is the shop page.")
14 
15 
16 tv = login(tv)
17 tv("SuperMan")

至關於把原有的tv替換掉了

下面展現真·終極形態：

 1 def login(obj_func):
 2     print("This is login page.")
 3     print("You had successed login!")
 4 
 5 @login
 6 def homepage():
 7     print("This is the homepage.")
 8 
 9 def tv(name):
10     print("This is the TV page.Hello %s"%name)
11 
12 def shop(name):
13     print("This is the shop page.")
14 
15 
16 #tv = login(tv)   再也不用傳入login()方法，直接使用tv()函數，便會自動包漿！
17 tv("SuperMan")

這種形式被稱之爲裝飾器

@login程序一執行，就會掃描裝飾器，至關於執行了tv = login(tv)

上面的程序均有錯誤，在須要擴展功能的函數上方，每個都要加@login才能夠，正確以下：

 1 def login(obj_func):
 2     def inner(arg):
 3         print("This is login page.")
 4         print("You had successed login!")
 5         obj_func(arg)   #tv()
 6     return inner
 7 
 8 
 9 @login
10 def homepage():
11     print("This is the homepage.")
12 @login
13 def tv(name):
14     print("This is the TV page.Hello %s" % name)
15 @login
16 def shop(name):
17     print("This is the shop page.")
18 
19 #tv = login(tv)
20 tv("SuperMan")

該段代碼的構造流程時：

一、在內存中定義login方法

二、遇到@login時，將login()下面的tv()方法傳入login()方法中做爲形參，遇到def inner(arg):方法後，在內存中定義inner()方法，return inner。

三、遇到tv("實參")後，直接去調用inner("形參")方法，執行了驗證，執行完驗證後，當遇到obj_func()arg後程序調至@login處，並將實參帶入tv()方法，執行結束

 

 1 def login(obj_func):
 2     def inner(*args):
 3         print("This is login page.")
 4         print("You had successed login!")
 5         obj_func(*args)   #tv()
 6     return inner
 7 
 8 
 9 @login
10 def homepage():
11     print("This is the homepage.")
12 @login
13 def tv(name,passwd):
14     print("This is the TV page.Hello %s\npassword is %s" % (name,passwd))
15     #print(type(args))
16 # 
17 # def tv(*args):
18 #     print("This is the TV page.Hello %s\npassword is %s" % args)
19 #     #print(type(args))
20 
21 @login
22 def shop(name):
23     print("This is the shop page.Hello %s"% name)
24 
25 #tv = login(tv)
26 tv('SuperMan','123456')
27 shop("daNiu")

 傳參裝飾器：

 1 print("111")
 2 def login():
 3     print("I'm the login() function")
 4 def errorHandle():
 5     print("I'm the errorHandle() function")
 6 
 7 def filter(func1,func2):
 8     def outer(args):
 9         def wrapper():
10             func1()
11             args()
12             func2()
13         return wrapper()
14     return outer
15 
16 @filter(login,errorHandle)
17 def index():
18     print("I'm the index() function.I also the main() function")