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 traceback from functools import wraps def 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 e if 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.py def skipper(func): ''' :param function func: :return: ''' func.__funskip__=True return func def classWrapper(commonDecoratorFunc): def innerMata(inClass): def collect_attrib(key, value, new_attrs): if hasattr(value, '__funskip__'): new_attrs[key] = value return if hasattr(value, '__func__') or isinstance(value, types.FunctionType): if isinstance(value, staticmethod): new_attrs[key] = staticmethod(commonDecoratorFunc(value.__func__)) return elif isinstance(value, classmethod): new_attrs[key] = classmethod(commonDecoratorFunc(value.__func__)) return elif 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 1/0 t=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, classWrapper import traceback from 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 inner if __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
1 EXCEPTION captured at function two EXCEPTION captured at function three Traceback (most recent call last): EXCEPTION captured at function four File "E:/pydev/异常处理装饰器.py", line 37, in inner EXCEPTION 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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 / 0 EXCEPTION captured at function pro ZeroDivisionError: integer division or modulo by zero EXCEPTION captured at function five Traceback (most recent call last): EXCEPTION captured at function five File "E:/pydev/异常处理装饰器.py", line 37, in inner EXCEPTION 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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 / 0 ZeroDivisionError: integer division or modulo by zero 1 1 Traceback (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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 / 0 ZeroDivisionError: integer division or modulo by zero Traceback (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 1/0 ZeroDivisionError: integer division or modulo by zero 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 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 / 0 ZeroDivisionError: integer division or modulo by zero 进程已结束,退出代码 1
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