python函數(shù)裝飾器用法實(shí)例詳解

本文實(shí)例講述了python函數(shù)裝飾器用法。分享給大家供大家參考。具體如下：
裝飾器經(jīng)常被用于有切面需求的場(chǎng)景，較為經(jīng)典的有插入日志、性能測(cè)試、事務(wù)處理等。裝飾器是解決這類問(wèn)題的絕佳設(shè)計(jì)，
有了裝飾器，我們就可以抽離出大量函數(shù)中與函數(shù)功能本身無(wú)關(guān)的雷同代碼并繼續(xù)重用。概括的講，裝飾器的作用就是為已經(jīng)存在的對(duì)象添加額外的功能。    
#! coding=utf-8
import time
def timeit(func):
  def wrapper(a):
    start = time.clock()
    func(1,2)
    end =time.clock()
    print 'used:', end - start
    print a
  return wrapper
@timeit
# foo = timeit(foo)完全等價(jià),
# 使用之后,foo函數(shù)就變了，相當(dāng)于是wrapper了
def foo(a,b):
  pass
#不帶參數(shù)的裝飾器
# wraper 將fn進(jìn)行裝飾，return wraper ,返回的wraper 就是裝飾之后的fn
def test(func):
  def wraper():
    print "test start"
    func()
    print "end start"
  return wraper
@test
def foo():
  print "in foo"
foo()

輸出：    
test start
in foo
end start

裝飾器修飾帶參數(shù)的函數(shù)：    
def parameter_test(func):
  def wraper(a):
    print "test start"
    func(a)
    print "end start"
  return wraper
@parameter_test
def parameter_foo(a):
  print "parameter_foo:"+a
#parameter_foo('hello')

輸出：    
>>>
test start
parameter_foo:hello
end start

裝飾器修飾不確定參數(shù)個(gè)數(shù)的函數(shù)：    
def much_test(func):
  def wraper(*args, **kwargs):
    print "test start"
    func(*args, **kwargs)
    print "end start"
  return wraper
@much_test
def much1(a):
  print a
@much_test
def much2(a,b,c,d ):
  print a,b,c,d
much1('a')
much2(1,2,3,4)

輸出：    
test start
a
end start
test start
1 2 3 4
end start

帶參數(shù)的裝飾器,再包一層就可以了：    
def tp(name,age):
  def much_test(func):
    print 'in much_test'
    def wraper(*args, **kwargs):
      print "test start"
      print str(name),'at:'+str(age)
      func(*args, **kwargs)
      print "end start"
    return wraper
  return much_test
@tp('one','10')
def tpTest(parameter):
  print parameter
tpTest('python....')

輸出：    
in much_test
test start
one at:10
python....
end start     
class locker:
  def __init__(self):
    print("locker.__init__() should be not called.")
  @staticmethod
  def acquire():
    print("locker.acquire() called.（這是靜態(tài)方法）")
  @staticmethod
  def release():
    print("locker.release() called.（不需要對(duì)象實(shí)例")
def deco(cls):
  '''cls 必須實(shí)現(xiàn)acquire和release靜態(tài)方法'''
  def _deco(func):
    def __deco():
      print("before %s called [%s]." % (func.__name__, cls))
      cls.acquire()
      try:
        return func()
      finally:
        cls.release()
    return __deco
  return _deco
@deco(locker)
def myfunc():
  print(" myfunc() called.")
myfunc()

輸出：
    
>>>
before myfunc called [__main__.locker].
locker.acquire() called.（這是靜態(tài)方法）
 myfunc() called.
locker.release() called.（不需要對(duì)象實(shí)例
>>>     
class mylocker:
  def __init__(self):
    print("mylocker.__init__() called.")
  @staticmethod
  def acquire():
    print("mylocker.acquire() called.")
  @staticmethod
  def unlock():
    print(" mylocker.unlock() called.")
class lockerex(mylocker):
  @staticmethod
  def acquire():
    print("lockerex.acquire() called.")
  @staticmethod
  def unlock():
    print(" lockerex.unlock() called.")
def lockhelper(cls):
  '''cls 必須實(shí)現(xiàn)acquire和release靜態(tài)方法'''
  def _deco(func):
    def __deco(*args, **kwargs):
      print("before %s called." % func.__name__)
      cls.acquire()
      try:
        return func(*args, **kwargs)
      finally:
        cls.unlock()
    return __deco
  return _deco
class example:
  @lockhelper(mylocker)
  def myfunc(self):
    print(" myfunc() called.")
  @lockhelper(mylocker)
  @lockhelper(lockerex)
  def myfunc2(self, a, b):
    print(" myfunc2() called.")
    return a + b
if __name__=="__main__":
  a = example()
  a.myfunc()
  print(a.myfunc())
  print(a.myfunc2(1, 2))
  print(a.myfunc2(3, 4))

輸出：
    
before myfunc called.
mylocker.acquire() called.
 myfunc() called.
 mylocker.unlock() called.
before myfunc called.
mylocker.acquire() called.
 myfunc() called.
 mylocker.unlock() called.
None
before __deco called.
mylocker.acquire() called.
before myfunc2 called.
lockerex.acquire() called.
 myfunc2() called.
 lockerex.unlock() called.
 mylocker.unlock() called.
3
before __deco called.
mylocker.acquire() called.
before myfunc2 called.
lockerex.acquire() called.
 myfunc2() called.
 lockerex.unlock() called.
 mylocker.unlock() called.
7
希望本文所述對(duì)大家的Python程序設(shè)計(jì)有所幫助。