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多重装饰器，即多个装饰器修饰同一个对象【实际上并非完全如此，且看下文详解】

1.装饰器无参数：

代码如下:

>>> def first(func):

print '%s() was post to first()'%func.func_name

def _first(*args,**kw):

print 'Call the function %s() in _first().'%func.func_name

return func(*args,**kw)

return _first

>>> def second(func):

print '%s() was post to second()'%func.func_name

def _second(*args,**kw):

print 'Call the function %s() in _second().'%func.func_name

return func(*args,**kw)

return _second

>>> @first

@second

def test():return 'hello world'

test() was post to second()

_second() was post to first()

>>> test()

Call the function _second() in _first().

Call the function test() in _second().

'hello world'

>>>

实际上它是相当于下面的代码：

代码如下:

>>> def test():

return 'hello world'

>>> test=second(test)

test() was post to second()

>>> test

<function _second at 0x000000000316D3C8>

>>> test=first(test)

_second() was post to first()

>>> test

<function _first at 0x000000000316D358>

>>> test()

Call the function _second() in _first().

Call the function test() in _second().

'hello world'

>>>

2.装饰器有参数：

代码如下:

>>> def first(printResult=False):

def _first(func):

print '%s() was post to _first()'%func.func_name

def __first(*args,**kw):

print 'Call the function %s() in __first().'%\

func.func_name

if printResult:

print func(*args,**kw),'#print in __first().'

else:

return func(*args,**kw)

return __first

return _first

>>> def second(printResult=False):

def _second(func):

print '%s() was post to _second()'%func.func_name

def __second(*args,**kw):

print 'Call the function %s() in __second().'%\

func.func_name

if printResult:

print func(*args,**kw),'#print in __second().'

else:

return func(*args,**kw)

return __second

return _second

>>> @first(True)

@second(True)

def test():

return 'hello world'

test() was post to _second()

__second() was post to _first()

>>> test()

Call the function __second() in __first().

Call the function test() in __second().

hello world #print in __second().

None #print in __first().

>>>

如上，第35行输出后调用__second()，而__second()中又调用了test()并print test()，而后返回__first()中继续执行print，而这个print语句print的内容是__second()返回的None

它等同于：

代码如下:

>>> def test():

return 'hello world'

>>> test=second(True)(test)

test() was post to _second()

>>>

>>> test

<function __second at 0x000000000316D2E8>

>>> test=first(True)(test)

__second() was post to _first()

>>> test

<function __first at 0x0000000003344C18>

>>>

3.多重装饰器的应用：

比如你是项目经理，你要求每一个代码块都必须有参数检查ArgsType和责任检查ResponsibilityRegister，这样就需要两个装饰器对此代码块进行监督。

代码如下:

#coding=utf-8

import os,sys,re

from collections import OrderedDict

def ArgsType(*argTypes,**kwTypes):

u'''ArgsType(*argTypes,**kwTypes)

options=[('opt_UseTypeOfDefaultValue',False)]

以下为本函数相关的开关，并非类型检验相关的关键字参数，所有options:

opt_UseTypeOfDefaultValue=>bool:False,为True时，将对没有指定类型的带默

认值的参数使用其默认值的类型

'''

def _ArgsType(func):

#确定所有的parameter name

argNames=func.func_code.co_varnames[:func.func_code.co_argcount]

#确定所有的default parameter

defaults=func.func_defaults

if defaults:

defaults=dict(zip(argNames[-len(defaults):],defaults))

else:defaults=None

#将“参数类型关键字参数”中的所有“options关键字参数”提出

options=dict()

for option,default in [('opt_UseTypeOfDefaultValue',False)]:

options[option]=kwTypes.pop(option,default)

#argTypes和kwTypes的总长度应该与argNames一致

if len(argTypes)+len(kwTypes)>len(argNames):

raise Exception('Too much types to check %s().'%func.func_name)

#所有kwTypes中的键不能覆盖在argTypes中已经占用的names

if not set(argNames[len(argTypes):]).issuperset(

set(kwTypes.keys())):

raise Exception('There is some key in kwTypes '+

'which is not in argNames.')

#确定所有的参数应该有的types

types=OrderedDict()

for name in argNames:types[name]=None

if len(argTypes):

for i in range(len(argTypes)):

name=argNames[i]

types[name]=argTypes[i]

else:

for name,t in kwTypes.items():

types[name]=t

if len(kwTypes):

for name,t in kwTypes.items():

types[name]=t

#关于default parameter的type

if options['opt_UseTypeOfDefaultValue']:

for k,v in defaults.items():

#如果default parameter的type没有另外指定，那么就使用

#default parameter的default value的type

if types[k]==None:

types[k]=type(v)

def __ArgsType(*args,**kw):

#order the args

Args=OrderedDict()

#init keys

for name in argNames:Args[name]=None

#init default values

if defaults is not None:

for k,v in defaults.items():

Args[k]=v

#fill in all args

for i in range(len(args)):

Args[argNames[i]]=args[i]

#fill in all keyword args

for k,v in kw.items():

Args[k]=v

#check if there is some None in the values

if defaults==None:

for k in Args:

if Args[k]==None:

if defaults==None:

raise Exception(('%s() needs %r parameter, '+

'which was not given')%(func.func_name,k))

else:

if not defaults.has_key(k):

raise Exception(('Parameter %r of %s() is'+

' not a default parameter')%\

(k,func.func_name))

#check all types

for k in Args:

if not isinstance(Args[k],types[k]):

raise TypeError(('Parameter %r of %s() must be '+

'a %r object, but you post: %r')%\

(k,func.func_name,types[k],Args[k]))

return func(*args,**kw)

return __ArgsType

return _ArgsType

def ResponsibilityRegister(author):

def _ResponsibilityRegister(func):

def __ResponsibilityRegister(*args,**kw):

try:

return func(*args,**kw)

except Exception as e:

print ("Something is wrong, It's %s's responsibility."%\

author).center(80,'*')

raise e

return __ResponsibilityRegister

return _ResponsibilityRegister

@ResponsibilityRegister('Kate')

@ArgsType(str,int)

def left(Str,Len=1):

return Str[:Len]

print 'Good calling:'

print left('hello world',8)

print 'Bad calling:'

print left(3,7)

这里没有文档，所以调用者不知道，使用了错误的调用，导致出错，这是Kate的责任。

像上面这种，对代码有两种互不相干的检验时，就可以使用多重装饰器。

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