Python 装饰器的作用

python装饰器的作用，我是这么理解的，

比如本来已经有几个写好的函数，这几个函数的返回值都是list，现在我想要它们都返回str型的值，一个个改函数太累，也容易出错，装饰器能解决这样的问题，它能对n个函数进行编程

 

def square(func):  
    #返回平方
    def _deco(a, b):  
        rtn = func(a, b)  
        return rtn * rtn  
    return _deco  
 
@square  
def my_add(a, b):  
    return a+b

print my_add(1,2)

 

 

# 原来的几个返回list的函数，具体干嘛不管，示例用
def even_element(lst):
    return [n for n in lst if n%2 == 0]

def odd_element(lst):
    return [n for n in lst if n%2 == 1]

def link_list(lst1, lst2):
    l = deepcopy(lst1)
    l.extend(lst2)
    return l

a = range(5)
b = range(10)

print even_element(a)
print odd_element(a)
print link_list(a, b)

 

 

 

from copy import deepcopy
# 用装饰器
def list_to_str(func):
    def wrapper(*args, **kwargs):
        rtn_lst = [str(n) for n in func(*args, **kwargs)]
        return ','.join(rtn_lst)
    return wrapper

# 此时这些函数都返回str型
@list_to_str
def even_element(lst):
    return [n for n in lst if n%2 == 0]

@list_to_str
def odd_element(lst):
    return [n for n in lst if n%2 == 1]

@list_to_str
def link_list(lst1, lst2):
    l = deepcopy(lst1)
    l.extend(lst2)
    return l


a = range(5)
b = range(10)

print even_element(a)
print odd_element(a)
print link_list(a, b)

 

带参数的装饰器

# encoding: utf-8

import time

'''
现实函数运行时间
参数run_times为被测函数运行次数
'''
def time_func(run_times):
    def _time_func(func):
        def wrapper(*args, **kwargs):
            t1 = time.time()
            for n in xrange(run_times):
                rtn = func(*args, **kwargs)
            t2 = time.time()
            print t2 - t1
            return rtn
        return wrapper
    return _time_func

@time_func(10000)
def addd(a, b):
    return a+b

print addd(1,2)