python中的函数修饰符
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python中的函数修饰符
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這是在Python學(xué)習(xí)小組上介紹的內(nèi)容，現(xiàn)學(xué)現(xiàn)賣、多練習(xí)是好的學(xué)習(xí)方式。
第一步：最簡單的函數(shù)，準(zhǔn)備附加額外功能
| 1 2 3 4 5 6 7 8 | # -*- coding:gbk -*- '''示例1: 最簡單的函數(shù),表示調(diào)用了兩次''' def myfunc(): ????print("myfunc() called.") myfunc() myfunc() |
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第二步：使用裝飾函數(shù)在函數(shù)執(zhí)行前和執(zhí)行后分別附加額外功能
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | # -*- coding:gbk -*- '''示例2: 替換函數(shù)(裝飾) 裝飾函數(shù)的參數(shù)是被裝飾的函數(shù)對象，返回原函數(shù)對象 裝飾的實(shí)質(zhì)語句: myfunc = deco(myfunc)''' def deco(func): ????print("before myfunc() called.") ????func() ????print("? after myfunc() called.") ????return func def myfunc(): ????print(" myfunc() called.") myfunc = deco(myfunc) myfunc() myfunc() |
第三步：使用語法糖@來裝飾函數(shù)
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | # -*- coding:gbk -*- '''示例3: 使用語法糖@來裝飾函數(shù)，相當(dāng)于“myfunc = deco(myfunc)” 但發(fā)現(xiàn)新函數(shù)只在第一次被調(diào)用，且原函數(shù)多調(diào)用了一次''' def deco(func): ????print("before myfunc() called.") ????func() ????print("? after myfunc() called.") ????return func @deco def myfunc(): ????print(" myfunc() called.") myfunc() myfunc() |
第四步：使用內(nèi)嵌包裝函數(shù)來確保每次新函數(shù)都被調(diào)用
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | # -*- coding:gbk -*- '''示例4: 使用內(nèi)嵌包裝函數(shù)來確保每次新函數(shù)都被調(diào)用， 內(nèi)嵌包裝函數(shù)的形參和返回值與原函數(shù)相同，裝飾函數(shù)返回內(nèi)嵌包裝函數(shù)對象''' def deco(func): ????def _deco(): ????????print("before myfunc() called.") ????????func() ????????print("? after myfunc() called.") ????????# 不需要返回func，實(shí)際上應(yīng)返回原函數(shù)的返回值 ????return _deco @deco def myfunc(): ????print(" myfunc() called.") ????return 'ok' myfunc() myfunc() |
第五步：對帶參數(shù)的函數(shù)進(jìn)行裝飾
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | # -*- coding:gbk -*- '''示例5: 對帶參數(shù)的函數(shù)進(jìn)行裝飾， 內(nèi)嵌包裝函數(shù)的形參和返回值與原函數(shù)相同，裝飾函數(shù)返回內(nèi)嵌包裝函數(shù)對象''' def deco(func): ????def _deco(a, b): ????????print("before myfunc() called.") ????????ret = func(a, b) ????????print("? after myfunc() called. result: %s" % ret) ????????return ret ????return _deco @deco def myfunc(a, b): ????print(" myfunc(%s,%s) called." % (a, b)) ????return a + b myfunc(1, 2) myfunc(3, 4) |
第六步：對參數(shù)數(shù)量不確定的函數(shù)進(jìn)行裝飾
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | # -*- coding:gbk -*- '''示例6: 對參數(shù)數(shù)量不確定的函數(shù)進(jìn)行裝飾， 參數(shù)用(*args, **kwargs)，自動適應(yīng)變參和命名參數(shù)''' def deco(func): ????def _deco(*args, **kwargs): ????????print("before %s called." % func.__name__) ????????ret = func(*args, **kwargs) ????????print("? after %s called. result: %s" % (func.__name__, ret)) ????????return ret ????return _deco @deco def myfunc(a, b): ????print(" myfunc(%s,%s) called." % (a, b)) ????return a+b @deco def myfunc2(a, b, c): ????print(" myfunc2(%s,%s,%s) called." % (a, b, c)) ????return a+b+c myfunc(1, 2) myfunc(3, 4) myfunc2(1, 2, 3) myfunc2(3, 4, 5) |
第七步：讓裝飾器帶參數(shù)
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | # -*- coding:gbk -*- '''示例7: 在示例4的基礎(chǔ)上，讓裝飾器帶參數(shù)， 和上一示例相比在外層多了一層包裝。 裝飾函數(shù)名實(shí)際上應(yīng)更有意義些''' def deco(arg): ????def _deco(func): ????????def __deco(): ????????????print("before %s called [%s]." % (func.__name__, arg)) ????????????func() ????????????print("? after %s called [%s]." % (func.__name__, arg)) ????????return __deco ????return _deco @deco("mymodule") def myfunc(): ????print(" myfunc() called.") @deco("module2") def myfunc2(): ????print(" myfunc2() called.") myfunc() myfunc2() |
第八步：讓裝飾器帶 類 參數(shù)
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | # -*- coding:gbk -*- '''示例8: 裝飾器帶類參數(shù)''' 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(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() myfunc() |
第九步：裝飾器帶類參數(shù)，并分拆公共類到其他py文件中，同時(shí)演示了對一個(gè)函數(shù)應(yīng)用多個(gè)裝飾器
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | # -*- coding:gbk -*- '''mylocker.py: 公共類 for 示例9.py''' 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 |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | # -*- coding:gbk -*- '''示例9: 裝飾器帶類參數(shù)，并分拆公共類到其他py文件中 同時(shí)演示了對一個(gè)函數(shù)應(yīng)用多個(gè)裝飾器''' from mylocker import * 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)) |
下面是參考資料，當(dāng)初有不少地方?jīng)]看明白，真正練習(xí)后才明白些：
1. Python裝飾器學(xué)習(xí) http://blog.csdn.net/thy38/article/details/4471421
2. Python裝飾器與面向切面編程 http://www.cnblogs.com/huxi/archive/2011/03/01/1967600.html
3. Python裝飾器的理解 http://apps.hi.baidu.com/share/detail/17572338
轉(zhuǎn)載于:https://www.cnblogs.com/chegnshi-coding/p/4457743.html
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