装饰器

装饰器要求接受一个callable对象，并返回一个callable对象

1、内置的装饰器

1.1 property

class Student(object):
  def __init__(self):
    super().__init__()
    self._score = None
  @property
  def score(self):
    return self._score
  @score.setter
  def score(self, value):
    if not isinstance(value, int):
      raise ValueError('score must be an integer!')
    if value < 0 or value > 100:
      raise ValueError('score must between 0 ~ 100!')
    self._score = value

2、自定义装饰器

2.1 函数装饰器

def log(func):
  def wrapper(*awg, **kw):
    if not callable(func):
      raise ValueError('function')
    print(func.__name__)
    return func()
  return wrapper
@log
def now():
  print(datetime.now())
now()
# 相当于 now = log(now)

2.2 类装饰器

实现call方法

class logging(object):
    def __init__(self, level='INFO'):
        self.level = level
    def __call__(self, func): # 接受函数
        def wrapper(*args, **kwargs):
            print "[{level}]: enter function {func}()".format(
                level=self.level,
                func=func.__name__)
            func(*args, **kwargs)
        return wrapper  #返回函数
@logging(level='INFO')
def say(something):
    print "say {}!".format(something)