python 装饰器

装饰器:由于函数是一个对象,而且函数对象可以被赋值给变量,所以,通过变量也能调用该函数:def now():  print '2013-120-25'now()f=nowprint ff()C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a6.py2013-120-25<function now at 0x0253FA70>2013-120-25现在,假设我们要增强now()函数的功能,比如,在函数调用前后自动打印日志,但又不希望修改now()函数的定义,这种在代码运行期间动态增加功能的方式,称之为“装饰器”（Decorator）。本质上,decorator 就是一个返回函数的高阶函数。所以，我们要定义一个能打印日志的decorator，可以定义如下：def wrapper(*args):    print '------------'    print args    print type(args)    print '------------'wrapper(1,2,3,4)C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a6.py------------(1, 2, 3, 4)<type 'tuple'>------------Process finished with exit code 0此时传入的是个元组def wrapper(**kw):    print '------------'    print kw    print type(kw)    print '------------'wrapper(size='large', quantity=6,sex='man')C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/a6.py------------{'quantity': 6, 'sex': 'man', 'size': 'large'}<type 'dict'>------------def log(func):    def wrapper(*args, **kw):        print 'call %s():' % func.__name__        return func(*args, **kw)    return wrapper@logdef now():    print '2013-12-25'now()C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/cookbook/a17.pycall now():2013-12-25