Emperor's New Clothes (understanding and use of Python decorators)

Today, say the decorator.

In the Python language, the main function of adorners is to reduce the essence of repetitive input. With an adorner, you can use repetitive code very intuitively and elegantly, like a dress that can be worn to the emperor or worn by anyone, as long as you feel the need for this "dress"

Syntax: @ DECORATION function name as @yifu is an adorner, Yifu is a decorative function

All right, let's do a dress first. (Cosmetic function):

def Yifu (func): #yifu是装饰函数名, Func is the emperor (the Decorated function), which together is called: The Emperor's New Clothes

Def Gongneng ():

Print ("I am a decorative feature")

Func ()

Return Gongneng

The clothes are ready to add a lot of function (Gongneng), such as bow tie and other related accessories

Now, who's going to wear this shirt? The emperor or anyone else.

Let's build a group of people:

Def people1 ():

Print ("I am a passer-by")

Def people2 ():

Print ("I am a passer-by")

Def people3 ():

Print ("I am a passer-by")

Def people4 ():

Print ("I'm a passer-by")

Find 4 people, now have clothes, also someone, clothes to who wear, casually

For a passer-by, just put a piece of clothing in front of a pedestrian's definition of a function:

@yifu

Def people1 ():

Print ("I am a passer-by")

To other people as well.

The person who added the clothes will output the function of the clothes and the function of passers-by, if other people also want this dress, all right, then give a piece.

As an example, a decorator (clothing) that calculates the time of the function execution can be used in a function that you like to use, just like a dress casually worn.

#皇帝的新衣: Function Adorner import timedef Yongshi (func): #这件衣服的功能是计算函数执行的时间 def baozhuang (): #这个功能是计算函数执行时间 Start=Time.clock () func () #这是要装饰的函数 end=Time.clock () print ('perform adorner function-time:', end-start)returnbaozhuangdef foo1 (): Print ('A foo1 function that has not been decorated is called') @yongshi #这个就是做好的装饰器了def foo2 (): Print ('the Foo2 function that has been decorated is called') #调用原来的函数foo1 () print ('-'* -) Foo2 ()

Summary: Python decorator is not a special cow function, just for the simplicity and elegance of the code, in a number of repeated use of a function, you can consider using the adorner to more concise expression, of course, you can wear many pieces of clothing, many times decorate, His basic idea is that Python can define functions in the function, which is quite special, the adorner is based on this function and was born. Fully embodies the idea that some data are objects.

Do you have an impulse to use?

Next time want to say what did not think well, want to write again. Python primer or relatively sour, cultivation in their own!!!!

Emperor's New Clothes (understanding and use of Python decorators)