[Python Advanced]002. Decorator (1)

Decorators (1)

• Introduced
• HelloWorld
  • Demand
  • Using functional programming
  • Add decorator
  • Analytical

Introduced

• The python decorator is called Decorator , which is to decorate a module.
• Action: Adds additional functionality to an existing object.
• Similar to annotations in Java, this method is decorated with @xxx in front of the method.
• Unlike annotations in Java, Python's adorners are fairly straightforward.
• Function-Type programming
• Slicing-oriented programming

HelloWorld demand

def Fun (i):     Print I

This is a simple method, and now we are going to execute some other code before and after executing this method, such as calculating the run time.
The Simple Way is:

Import  Time def Fun (i):     = time.time ()    print  i    = Time.time ()-T     #  calculate run time    Print ' Run Time: ', str (t)    #  print Time

This method is inconvenient and cannot be reused.

Using functional programming

Import Time#Calculate run TimedefExec_time (FN, i):#fn: method; I: Parameters of the methodt =time.time () fn (i)#call FNt = time.time ()-T#Calculate run Time    Print 'Run Time:', str (t)#Print TimedefFun (i):PrintI#calledExec_time (fun, i)

In this way, in the actual invocation, it is necessary to wrap a layer exec_time of method, although it can be reused, but it is not flexible.

Add decorator

Now we're going to add modifiers.

 fromFunctoolsImportWraps#introduce the package required by the adornerImport Time#define an adornerdefExec_time (FN):#parameter fn: The method to be modified is our fun@wraps (FN)def_ (i):#modification Method, parameter I is fun to pass over the parameterst =time.time () fn (i)#Execution Methodt = time.time ()-TPrint 'Run Time:', str (t)return_#returns the post-decoration method

This completes an adorner that calculates the run time.

@exec_time def Fun (i):     Print I@exec_time def fun2 (i):     Print ' fun2 ', I

It is very convenient to use.

Analytical

• @exec_timeafter the method is added fun , the equivalent method is called automatically when the call is made exec_time(fun) .
• funThe method is exec_time decorated, the method is timed at the beginning and end, and the print takes time, which is a cross section, which is the way of programming 面向切面的编程 . The horizontal insertion of logic during method execution can reduce duplication of code in many places.

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Reprinted from "Baby bus Superdo Team" original link: http://www.cnblogs.com/superdo/p/4829345.html

[Python Advanced]002. Decorator (1)