Decorator functions and the use of class decorators

One 、 Decorator

Decorator ： Decorating functions and classes , effect ： Extend and enhance functions and classes

Two 、 The classification of decorators

Two categories: ： Decorator functions and decorator classes

3、 ... and 、 Decorator function definition and Application

 function ： The smallest unit of encapsulated code , Provide code reusability 
 Decorator functions take advantage of some features of functions ：
1、 The function can be used as an argument 
3、 Functions can be variables 
2、 Function can also return function 
 Decorator function essence ： Call the built-in method of decoration function 

Four 、 Use of decorator functions

import time

def display_time(fun):
    def wrapper():
        t1 = time.time()
        resutl =fun()
        t2 = time.time()
        print(" The total time is {:.4} s".format(t2 - t1))
        return resutl
    return wrapper

def is_price(num):
    if num < 2:
        return False
    elif num == 2:
        return True
    else:
        for i in range(2, num):
            if num % i == 0:
                return False
        return True

'''
 Compared with the front , More return value ,
 Need to be in display_time Add... To the function fun() Return results 
'''
@display_time
def count_prime_number():
    count=0
    for i in range(2, 1000):
        if is_price(i):
            count=count+1
    return count


counts=count_prime_number()
print(counts)

5、 ... and 、 The use of class decorators

import time
#  Define decoration class ‐‐‐‐‐》 Essential class   effect ： Original function + Extend the functionality 
class A:
    #  Original function  self._func()
    def __init__(self, func):
        self._func = func
    #  Extend the functionality 
    def __call__(self, *args, **kwargs):
        """
        __call__ function ： Instantiate objects ()
        :return:
        """
        start = time.time()
        #  Original function 
        result=self._func(*args, **kwargs)  #  Original function 
        end = time.time()

        print(" The total time is {:.4} s".format(end - start))
        return result

@A
def count_prime_number(maxnumber):
    time.sleep(1)
    sum=0
    for i in range(2, maxnumber):
            sum=sum+i
    return sum

sums=count_prime_number(10000)
print(sums)