#decorator.py
def makeHtmlTag(tag, *args, **kwds):
    def real_decorator(fn):
        css_class = " class='{0}'".format(kwds["css_class"]) \
                                 if "css_class" in kwds else ""
        def wrapped(*args, **kwds):
            return "<"+tag+css_class+">" + fn(*args, **kwds) + "</"+tag+">"
        return wrapped
    # return decorator dont call it
    return real_decorator

@makeHtmlTag(tag="b", css_class="bold_css")
@makeHtmlTag(tag="i", css_class="italic_css")
def hello():
    return "hello world"

print hello()

也可以在类中编写decorator

#class.py
class makeHtmlTagClass(object):
    def __init__(self, tag, css_class=""):
        self._tag = tag
        self._css_class = " class='{0}'".format(css_class) \
                                       if css_class != "" else ""

    def __call__(self, fn):
        def wrapped(*args, **kwargs):
            return "<" + self._tag + self._css_class+">"  \
                       + fn(*args, **kwargs) + "</" + self._tag + ">"
        return wrapped

@makeHtmlTagClass(tag="b", css_class="bold_css")
@makeHtmlTagClass(tag="i", css_class="italic_css")
def hello(name):
    return "Hello, {}".format(name)

print hello("Your name")

说到计数器示例-如上所述，计数器将在使用decorator的所有函数之间共享：

def counter(func):
    def wrapped(*args, **kws):
        print 'Called #%i' % wrapped.count
        wrapped.count += 1
        return func(*args, **kws)
    wrapped.count = 0
    return wrapped

这样，您的装饰器可以重复用于不同的函数（或用于多次装饰同一个函数：func_counter1=counter（func）；func_counter2=counter（func）），并且计数器变量将对每个变量保持私有。

装饰器接受函数定义并创建一个新函数，该函数执行该函数并转换结果。

@deco
def do():
    ...

相当于：

do = deco(do)

例子：

def deco(func):
    def inner(letter):
        return func(letter).upper()  #upper
    return inner

This

@deco
def do(number):
    return chr(number)  # number to letter

相当于这个

def do2(number):
    return chr(number)

do2 = deco(do2)

65<=>“a”

print(do(65))
print(do2(65))
>>> B
>>> B

要理解decorator，需要注意的是，decorator创建了一个新的函数do，它在内部执行函数并转换结果。

这里是一个链接装饰器的简单示例。注意最后一行-它显示了封面下的情况。

############################################################
#
#    decorators
#
############################################################

def bold(fn):
    def decorate():
        # surround with bold tags before calling original function
        return "<b>" + fn() + "</b>"
    return decorate


def uk(fn):
    def decorate():
        # swap month and day
        fields = fn().split('/')
        date = fields[1] + "/" + fields[0] + "/" + fields[2]
        return date
    return decorate

import datetime
def getDate():
    now = datetime.datetime.now()
    return "%d/%d/%d" % (now.day, now.month, now.year)

@bold
def getBoldDate(): 
    return getDate()

@uk
def getUkDate():
    return getDate()

@bold
@uk
def getBoldUkDate():
    return getDate()


print getDate()
print getBoldDate()
print getUkDate()
print getBoldUkDate()
# what is happening under the covers
print bold(uk(getDate))()

输出如下所示：

17/6/2013
<b>17/6/2013</b>
6/17/2013
<b>6/17/2013</b>
<b>6/17/2013</b>

做同样事情的另一种方式：

class bol(object):
  def __init__(self, f):
    self.f = f
  def __call__(self):
    return "<b>{}</b>".format(self.f())

class ita(object):
  def __init__(self, f):
    self.f = f
  def __call__(self):
    return "<i>{}</i>".format(self.f())

@bol
@ita
def sayhi():
  return 'hi'

或者，更灵活地说：

class sty(object):
  def __init__(self, tag):
    self.tag = tag
  def __call__(self, f):
    def newf():
      return "<{tag}>{res}</{tag}>".format(res=f(), tag=self.tag)
    return newf

@sty('b')
@sty('i')
def sayhi():
  return 'hi'

#decorator.py
def makeHtmlTag(tag, *args, **kwds):
    def real_decorator(fn):
        css_class = " class='{0}'".format(kwds["css_class"]) \
                                 if "css_class" in kwds else ""
        def wrapped(*args, **kwds):
            return "<"+tag+css_class+">" + fn(*args, **kwds) + "</"+tag+">"
        return wrapped
    # return decorator dont call it
    return real_decorator

@makeHtmlTag(tag="b", css_class="bold_css")
@makeHtmlTag(tag="i", css_class="italic_css")
def hello():
    return "hello world"

print hello()

也可以在类中编写decorator

#class.py
class makeHtmlTagClass(object):
    def __init__(self, tag, css_class=""):
        self._tag = tag
        self._css_class = " class='{0}'".format(css_class) \
                                       if css_class != "" else ""

    def __call__(self, fn):
        def wrapped(*args, **kwargs):
            return "<" + self._tag + self._css_class+">"  \
                       + fn(*args, **kwargs) + "</" + self._tag + ">"
        return wrapped

@makeHtmlTagClass(tag="b", css_class="bold_css")
@makeHtmlTagClass(tag="i", css_class="italic_css")
def hello(name):
    return "Hello, {}".format(name)

print hello("Your name")