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Python類中的裝飾器在當(dāng)前類中的聲明與調(diào)用詳解

更新時(shí)間：2020年04月15日 09:23:49 作者：天外歸云

這篇文章主要介紹了Python類中的裝飾器在當(dāng)前類中的聲明與調(diào)用詳解，具有很好的參考價(jià)值，希望對大家有所幫助。一起跟隨小編過來看看吧

我的Python環(huán)境：3.7

在Python類里聲明一個(gè)裝飾器，并在這個(gè)類里調(diào)用這個(gè)裝飾器。

代碼如下：

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} ')

注意：

1. 其中裝飾器test是在類Test中聲明并在其方法test_a中調(diào)用

2. 裝飾器test內(nèi)層wrapper函數(shù)的首參數(shù)是self

補(bǔ)充知識(shí)：python-類內(nèi)函數(shù)的全局裝飾器

有時(shí)，比如寫RF的測試庫的時(shí)候，很多方法都寫在一個(gè)類里。我們又可能需要一個(gè)通用的裝飾器，比如，要給某個(gè)底層類的方法打樁，查看入?yún)⒑统鰠?，用以理解業(yè)務(wù)；或者要hold住所有的執(zhí)行錯(cuò)誤，打印堆棧又不想程序退出或用例直接失敗

比如捕捉錯(cuò)誤的裝飾器

import traceback
from functools import wraps


def trier(soft=False):
  '''
  :param bool soft: 為True時(shí)，打印報(bào)錯(cuò)堆棧并忽略異常。默認(rèn)False，打印報(bào)錯(cuò)堆棧并拋出異常
  :return:
  如果要給類方法、靜態(tài)方法裝飾，則該裝飾器必須處于比@staticmethod裝飾器更內(nèi)一層才行
  '''
  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

或者參數(shù)跟蹤的裝飾器

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

這類裝飾器經(jīng)常會(huì)給類里的每個(gè)函數(shù)都使用

每次都裝飾的話，也挺麻煩

python里可以給類寫個(gè)裝飾器，所以可以輸入一個(gè)類，返回一個(gè)新類，這個(gè)新類擁有原來類里的所有方法，但所有方法都被裝飾

使用元類，可以做到這一點(diǎn)。

目前可以批量裝飾普通方法、靜態(tài)方法、類方法、屬性，暫不支持__init__和__del__之類的特殊方法，以免出現(xiàn)意外的問題。

目前類B使用了全局裝飾器，假如類B繼承自類A，類C繼承自類B

則類B、類C內(nèi)的所有方法都被全局裝飾（全局裝飾可以被繼承）

且類B繼承自類A的所有方法也會(huì)被全局裝飾

但這種裝飾不會(huì)影響到類A，調(diào)用類A下的方法時(shí)，所有方法都不被裝飾

經(jīng)過多次嘗試，最后的實(shí)現(xiàn)代碼如下

# 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):
          # 當(dāng)對property類進(jìn)行重組的時(shí)候，我們強(qiáng)制裝飾了property類的fget fset和fdel方法。但是，不是每個(gè)propery都有這三個(gè)方法，有些是None，強(qiáng)制裝飾會(huì)報(bào)錯(cuò)，所以我們這里要考慮提前返回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提供了一個(gè)后門，被skipper裝飾的函數(shù)會(huì)跳過全局裝飾器

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()

執(zhí)行結(jié)果如圖

一個(gè)更完整的示例

from clswrapper那個(gè)文件 import skipper, classWrapper
import traceback
from functools import wraps

'''為簡潔起見，這次我們用的是不帶參數(shù)的trier裝飾器'''
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))替換，則可以不拋出異常
  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被跳過，所以沒有被里層捕獲，才會(huì)不打堆棧直接走到這里")
 
  print("最后這個(gè)會(huì)真正觸發(fā)異常，因?yàn)閙obj實(shí)例并沒有被裝飾過")
  m=mobj()
  time.sleep(1)
  m.five()

它展示了這個(gè)強(qiáng)大裝飾器能處理的各種情況，執(zhí)行結(jié)果應(yīng)該如下

1
EXCEPTION captured at function two
EXCEPTION captured at function three
Traceback (most recent call last):
EXCEPTION captured at function four
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
EXCEPTION captured at function one
  return func(*args, **kwargs)
EXCEPTION captured at function five
 File "E:/pydev/異常處理裝飾器.py", line 138, in two
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 129, in three
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.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/異常處理裝飾器.py", line 37, in inner
EXCEPTION captured at function seven
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 115, in one
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 104, in five
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.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/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 104, in five
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 104, in five
  w = 1 / 0
ZeroDivisionError: integer division or modulo by zero

Traceback (most recent call last):
 File "E:/pydev/異常處理裝飾器.py", line 37, in inner
  return func(*args, **kwargs)
 File "E:/pydev/異常處理裝飾器.py", line 157, in seven
  return 1/0
ZeroDivisionError: integer division or modulo by zero

c.eight被跳過，所以沒有被里層捕獲，才會(huì)不打堆棧直接走到這里
最后這個(gè)會(huì)真正觸發(fā)異常，因?yàn)閙obj實(shí)例并沒有被裝飾過
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

進(jìn)程已結(jié)束，退出代碼 1

以上這篇Python類中的裝飾器在當(dāng)前類中的聲明與調(diào)用詳解就是小編分享給大家的全部內(nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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