Python Road, Day4-python Foundation 4

The content of this section

1. Iterators & Generators
2. Decorative Device
3. Json & Pickle Data serialization
4. Software Catalog Structure specification
5. Jobs: ATM Project development

1. Decorator (grammar sugar)

Definition: The essence is a function, (decorating other functions), is to add additional functions for other functions

Principle:

1. Cannot modify the source code of the decorated function
2. Cannot modify the calling method of the decorated function

Implement the adorner "knowledge" reserve:

1. function is "variable"

2. Higher-order functions

A. Passing a function name as an argument to another function (adding functionality to a decorated function without modifying its source code)

def bar ():    print ("in the Bar") def test1 (func):   #test1 (bar)    print (func) func () #相当于bar ()    test1 (BAR) # This is equivalent to  func=bar--------output--------<function bar at 0x05604300>in the bar

1 Import Time2 defBar ():3Time.sleep (3)4     Print("In the bar")5 defDeco (func):6Start_time=time.time ()7 func ()8Stop_time=time.time ()9     Print("The func run time is%s"% (stop_time-start_time))TenDeco (BAR)#But this example is not appropriate because it changes the way it is called One #Bar () that's the way it used to be called. A  -------Output----- - inchThe bar theThe Func run time is3.0007259845733643

Example

B. The return value contains the function name (does not modify the function call method)

1 defBar ():2     Print("In the bar")3 defDeco (func):#Func=bar4     Print(func)#Print bar's memory address5     returnFunc#then return to the memory address of Bar6         #memory address + () to run7 8Deco (BAR)#Pass memory address as function name to Deco9 Print("----Split Line---")Ten Print(Deco (BAR))#print out the return value One Print("------|| ------") ADeco (Bar ())#Pass the return value to Deco, which does not conform to the definition of the higher order function -  -----------output------ the<function Bar at 0x058c4228> -----Split Line--- -<function Bar at 0x058c4228> -<function Bar at 0x058c4228> +------|| ------ - inchThe bar +None

View Code

Therefore, you can get the practice without changing the calling method

def bar ():    print ("in the Bar") def deco (func):   #func =bar    Print (func)   #打印bar的内存地址    return func    #再返回bar的内存地址        #内存地址 + () will be able to run the Bar=deco (bar)  #将return返回的值赋值给barbar ()     #此时bar为内存地址, so bar+ () Can run bar this function------output-----<function bar at 0x05814150>in the bar

3. Nesting functions

Definition: In a function body, use DEF to declare a new function. Instead of calling him.

def foo ():    print ("in the Foo")    def Bar ():        print ("in the bar/")    bar ()   #局部变量只能在局部函数内调用foo () "Def Foo ():    bar ()  #这种是直接调用 "-------output----in the Fooin the bar/

4. High-order function + nested function = = "Adorner"

anonymous functions

Def plus (n):     #函数名plus    return n+1 plus2 = lambda x:x+1   #没有函数名字, only variable name # but the two get the same result #lambda X:x+1 has a name called Plus2. , equivalent to Def plus2 (x)

Python Road, Day4-python Foundation 4