Python类中的装饰器在当前类中的声明与调用详解
(编辑：jimmy 日期: 2024/11/12 浏览：2)
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/", line 212, in <module> m.five() File "E:/pydev/", 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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