Python类中的装饰器在当前类中的声明与调用详解

我的Python环境：3.7

在Python类里声明一个装饰器，并在这个类里调用这个装饰器。

代码如下：

class Test(): xx = False def __init__(self): pass def test(func): def wrapper(self, *args, **kwargs): print(self.xx) return func(self, *args, **kwargs) return wrapper @test def test_a(self,a,b): print(f’ok,{a} {b}’)

注意：

1. 其中装饰器test是在类Test中声明并在其方法test_a中调用

2. 装饰器test内层wrapper函数的首参数是self

补充知识：python-类内函数的全局装饰器

有时，比如写RF的测试库的时候，很多方法都写在一个类里。我们又可能需要一个通用的装饰器，比如，要给某个底层类的方法打桩，查看入参和出参，用以理解业务；或者要hold住所有的执行错误，打印堆栈又不想程序退出或用例直接失败

比如捕捉错误的装饰器

import tracebackfrom functools import wrapsdef trier(soft=False): ’’’ :param bool soft: 为True时，打印报错堆栈并忽略异常。默认False，打印报错堆栈并抛出异常 :return: 如果要给类方法、静态方法装饰，则该装饰器必须处于比@staticmethod装饰器更内一层才行 ’’’ def realTrier(func): ’’’ :param function func: :return: ’’’ @wraps(func) # 保留__name__ __doc__ __module__ def innerfunc(*args, **kwargs): try:return func(*args, **kwargs) except Exception, e:try: print(traceback.format_exc())except: print eif not soft: raise return innerfunc return realTrier

或者参数跟踪的装饰器

def tracer(func): def infunc(*args, **kwargs): print func.__name__, args, kwargs res=infunc(*args, **kwargs) print func.__name__, res return res

这类装饰器经常会给类里的每个函数都使用

每次都装饰的话，也挺麻烦

python里可以给类写个装饰器，所以可以输入一个类，返回一个新类，这个新类拥有原来类里的所有方法，但所有方法都被装饰

使用元类，可以做到这一点。

目前可以批量装饰普通方法、静态方法、类方法、属性，暂不支持__init__和__del__之类的特殊方法，以免出现意外的问题。

目前类B使用了全局装饰器，假如类B继承自类A，类C继承自类B

则类B、类C内的所有方法都被全局装饰（全局装饰可以被继承）

且类B继承自类A的所有方法也会被全局装饰

但这种装饰不会影响到类A，调用类A下的方法时，所有方法都不被装饰

经过多次尝试，最后的实现代码如下

# clswrapper.pydef skipper(func): ’’’ :param function func: :return: ’’’ func.__funskip__=True return funcdef classWrapper(commonDecoratorFunc): def innerMata(inClass): def collect_attrib(key, value, new_attrs): if hasattr(value, ’__funskip__’):new_attrs[key] = valuereturn if hasattr(value, ’__func__’) or isinstance(value, types.FunctionType):if isinstance(value, staticmethod): new_attrs[key] = staticmethod(commonDecoratorFunc(value.__func__)) returnelif isinstance(value, classmethod): new_attrs[key] = classmethod(commonDecoratorFunc(value.__func__)) returnelif not key.startswith(’__’): new_attrs[key] = commonDecoratorFunc(value) return else:if isinstance(value, property): # 当对property类进行重组的时候，我们强制装饰了property类的fget fset和fdel方法。但是，不是每个propery都有这三个方法，有些是None，强制装饰会报错，所以我们这里要考虑提前返回None propertyWrapper = property(fget=commonDecoratorFunc(value.fget) if value.fget else None,fset=commonDecoratorFunc(value.fset) if value.fset else None,fdel=commonDecoratorFunc(value.fdel) if value.fdel else None,doc=value.__doc__) new_attrs[key] = propertyWrapper return new_attrs[key] = value class Meta(type): @classmethod def options(cls, bases, attrs):new_attrs = {}for key, value in attrs.items(): collect_attrib(key, value, new_attrs)for base in bases: for mbase in base.mro(): for key, value in mbase.__dict__.items(): if key not in new_attrs:collect_attrib(key, value, new_attrs)return new_attrs def __new__(cls, name, bases, attrs):new_attrs = cls.options(bases, attrs)return super(Meta, cls).__new__(cls, name, bases, new_attrs) return six.add_metaclass(Meta)(inClass) return innerMata

其中，skipper提供了一个后门，被skipper装饰的函数会跳过全局装饰器

使用方法如下

@classWrapper(trier(soft=True))class Tree(object): @skipper def div(self): return 1/0 def divsafe(self): return 1/0t=Tree()print t.divsafe()print t.div()

执行结果如图

一个更完整的示例

from clswrapper那个文件 import skipper, classWrapperimport tracebackfrom functools import wraps’’’为简洁起见，这次我们用的是不带参数的trier装饰器’’’def trier(func): @wraps(func) def inner(*args, **kwargs): try: return func(*args, **kwargs) except: print('EXCEPTION captured at function %s' % func.__name__, file=sys.stderr) print(traceback.format_exc().decode('gbk')) raise return innerif __name__=='__main__': import time class mobj(object): def five(self): w = 1 / 0 class obj(mobj): def __init__(self): # print 'obj.__init__' return @classmethod def one(self): w = 1 / 0 print(’obj.one’) @classWrapper(trier) # 或者用@classWrapper(argTrier(True))替换，则可以不抛出异常 class obj1(obj): aa = 1 def __init__(self): super(obj1, self).__init__() self.var = 1 @classmethod def three(cls): w = 1 / 0 print(’obj1.three’) @staticmethod def four(): w = 1 / 0 print(’obj1.four’) def two(self): w = 1 / 0 print(self.pro) print(’obj1.two’) @property def pro(self): return self.var @pro.setter def pro(self, value): self.var = value / 0 @skipper def eight(self): w=1/0 return w class outerobj(obj1): def seven(self): return 1/0 b = obj1() a = obj1 print(b.var) try: b.two() except: pass try: a.three() except: pass try: a.four() except: pass try: a.one() except: pass try: b.five() except: pass try: b.pro = 3 except: pass print(b.pro) print(a.aa) c=outerobj() try: c.five() except: pass try: c.seven() except: pass try: c.eight() except: print('c.eight被跳过，所以没有被里层捕获，才会不打堆栈直接走到这里') print('最后这个会真正触发异常，因为mobj实例并没有被装饰过') m=mobj() time.sleep(1) m.five()

它展示了这个强大装饰器能处理的各种情况，执行结果应该如下

1EXCEPTION captured at function twoEXCEPTION captured at function threeTraceback (most recent call last):EXCEPTION captured at function four File 'E:/pydev/异常处理装饰器.py', line 37, in innerEXCEPTION captured at function one return func(*args, **kwargs)EXCEPTION captured at function five File 'E:/pydev/异常处理装饰器.py', line 138, in two w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 129, in three w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 134, in four w = 1 / 0EXCEPTION captured at function proZeroDivisionError: integer division or modulo by zeroEXCEPTION captured at function fiveTraceback (most recent call last):EXCEPTION captured at function five File 'E:/pydev/异常处理装饰器.py', line 37, in innerEXCEPTION captured at function seven return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 115, in one w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 104, in five w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 148, in pro self.var = value / 0ZeroDivisionError: integer division or modulo by zero11Traceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 104, in five w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 104, in five w = 1 / 0ZeroDivisionError: integer division or modulo by zeroTraceback (most recent call last): File 'E:/pydev/异常处理装饰器.py', line 37, in inner return func(*args, **kwargs) File 'E:/pydev/异常处理装饰器.py', line 157, in seven return 1/0ZeroDivisionError: integer division or modulo by zeroc.eight被跳过，所以没有被里层捕获，才会不打堆栈直接走到这里最后这个会真正触发异常，因为mobj实例并没有被装饰过Traceback (most recent call last): File 'E:/pydev/�쳣����װ����.py', line 212, in <module> m.five() File 'E:/pydev/�쳣����װ����.py', line 104, in five w = 1 / 0ZeroDivisionError: integer division or modulo by zero进程已结束，退出代码 1

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