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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: 2024/11/18 浏览：3 次 )

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

Python类中的装饰器在当前类中的声明与调用详解

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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