1.通过函数定义装饰器

class MyObj:
    def __init__(self, value):
        self.value = value;
        
    def set_value(self, value):
        print("set value:",value)
        self.value = value
    def get_set_value_name(self):
        print(self.set_value.__name__)
        
o = MyObj(10)
o.set_value(12)
o.get_set_value_name()

# 想在set_value之前打印一个日志

def log(f):
    def w(*args, **kwargs):
        print("begin to log")
        return f(*args, **kwargs)
    return w

class MyObj:
    def __init__(self, value):
        self.value = value;
    @log # 等同于 set_value = log(set_value)
    def set_value(self, value):
        print(set_value.__name__)
        print("set value:",value)
        self.value = value
    def get_set_value_name(self):
        print(self.set_value.__name__)
        
o = MyObj(10)
o.set_value(120)
o.get_set_value_name()


# 定义带入参的装饰器

def log(text):
    def decorator(func):
        def wrapper(*args, **kw):
            print('%s %s():' % (text, func.__name__))
            return func(*args, **kw)
        return wrapper
    return decorator

class MyObj:
    def __init__(self, value):
        self.value = value;
        
    @log("MyObj") # 等同于 set_value = log('MyObj')(set_value)
    def set_value(self, value):
        print("set value:",value)
        self.value = value
    
    def get_set_value_name(self):
        print(self.set_value.__name__)
        
o = MyObj(10)
o.set_value(120)
o.get_set_value_name()

# set_value的函数签名被修改了， 对于依赖函数签名的代码将报错
# 不需要编写wrapper.__name__ = func.__name__这样的代码
# 可使用Python内置的functools.wraps模块
# 定义带入参的装饰器
import functools

def log(text):
    def decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kw):
            print('%s %s():' % (text, func.__name__))
            return func(*args, **kw)
        return wrapper
    return decorator

class MyObj:
    def __init__(self, value):
        self.value = value;
        
    @log("MyObj") # 等同于 set_value = log('MyObj')(set_value)
    def set_value(self, value):
        print("set value:",value)
        self.value = value
    
    def get_set_value_name(self):
        print(self.set_value.__name__)
        
o = MyObj(10)
o.set_value(120)
o.get_set_value_name()

输出

set value: 12
set_value
begin to log
set_value
set value: 120
w
MyObj set_value():
set value: 120
wrapper
MyObj set_value():
set value: 120
set_value

2.定义装饰器类

# 装饰器类
class logit(object):
    def __init__(self, logfile='out.log'):
        self.logfile = logfile
 
    def __call__(self, func):
        @functools.wraps(func)
        def wrapped_function(*args, **kwargs):
            log_string = func.__name__ + " was called"
            print(log_string)
            # 打开logfile并写入
            with open(self.logfile, 'a') as opened_file:
                # 现在将日志打到指定的文件
                opened_file.write(log_string + '\n')
            # 现在，发送一个通知
            self.notify()
            return func(*args, **kwargs)
        return wrapped_function
 
    def notify(self):
        # 此时logit只打日志，不做别的，若需要发送通知只需要继承该类实现此方法即可
        pass
    
@logit()
def do_nothing():
    pass

do_nothing()

输出

do_nothing was called

参考资料

• 1.Python 函数装饰器
  (opens new window)
• 2.装饰器
  (opens new window)

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