裝飾器經(jīng)常被用于有切面需求的場景，較為經(jīng)典的有插入日志、性能測試、事務(wù)處理等。裝飾器是解決這類問題的絕佳設(shè)計，
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, 
# 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.（不需要對象實例") 
def deco(cls): 
  '''cls 必須實現(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.（不需要對象實例
>>>

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

希望本文所述對大家的Python程序設(shè)計有所幫助。

您可能感興趣的文章: