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August 25, 2014 06:25
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python decorator demo
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#! /usr/bin/env python | |
#coding=utf-8 | |
#from http://www.cnblogs.com/rhcad/archive/2011/12/21/2295507.html | |
#第一步:最简单的函数,准备附加额外功能 | |
def test1(): | |
'''示例1: 最简单的函数,表示调用了两次''' | |
def myfunc(): | |
print("myfunc() called.") | |
myfunc() | |
myfunc() | |
#第二步:使用装饰函数在函数执行前和执行后分别附加额外功能 | |
def test2(): | |
'''示例2: 替换函数(装饰) | |
装饰函数的参数是被装饰的函数对象,返回原函数对象 | |
装饰的实质语句: 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:使用语法糖@来装饰函数 | |
def test3(): | |
'''示例3: 使用语法糖@来装饰函数,相当于“myfunc = deco(myfunc)” | |
但发现新函数只在第一次被调用,且原函数多调用了一次''' | |
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:使用内嵌包装函数来确保每次新函数都被调用 | |
def test4(): | |
'''示例4: 使用内嵌包装函数来确保每次新函数都被调用, | |
内嵌包装函数的形参和返回值与原函数相同,装饰函数返回内嵌包装函数对象''' | |
def deco(func): | |
def _deco(): | |
print("before myfunc() called.") | |
func() | |
print(" after myfunc() called.") | |
# 不需要返回func,实际上应返回原函数的返回值 | |
return _deco | |
@deco | |
def myfunc(): | |
print(" myfunc() called.") | |
return 'ok' | |
myfunc() | |
myfunc() | |
#第五步:对带参数的函数进行装饰 | |
def test5(): | |
'''示例5: 对带参数的函数进行装饰, | |
内嵌包装函数的形参和返回值与原函数相同,装饰函数返回内嵌包装函数对象''' | |
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:对参数数量不确定的函数进行装饰 | |
def test6(): | |
'''示例6: 对参数数量不确定的函数进行装饰, | |
参数用(*args, **kwargs),自动适应变参和命名参数''' | |
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:让装饰器带参数 | |
def test7(): | |
'''示例7: 在示例4的基础上,让装饰器带参数, | |
和上一示例相比在外层多了一层包装。 | |
装饰函数名实际上应更有意义些''' | |
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:让装饰器带 类 参数 | |
def test8(): | |
'''示例8: 装饰器带类参数''' | |
class locker: | |
def __init__(self): | |
print("locker.__init__() should be not called.") | |
@staticmethod | |
def acquire(): | |
print("locker.acquire() called.(这是静态方法)") | |
@staticmethod | |
def release(): | |
print(" locker.release() called.(不需要对象实例)") | |
def deco(cls): | |
'''cls 必须实现acquire和release静态方法''' | |
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:装饰器带类参数,并分拆公共类到其他py文件中,同时演示了对一个函数应用多个装饰器 | |
def test9(): | |
'''mylocker.py: 公共类 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 必须实现acquire和release静态方法''' | |
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 | |
'''示例9: 装饰器带类参数,并分拆公共类到其他py文件中 | |
同时演示了对一个函数应用多个装饰器''' | |
#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 | |
a = example() | |
a.myfunc() | |
print(a.myfunc()) | |
print(a.myfunc2(1, 2)) | |
print(a.myfunc2(3, 4)) | |
print "-----test1-----" | |
test1() | |
print "\n-----test2-----" | |
test2() | |
print "\n-----test3-----" | |
test3() | |
print "\n-----test4-----" | |
test4() | |
print "\n-----test5-----" | |
test5() | |
print "\n-----test6-----" | |
test6() | |
print "\n-----test7-----" | |
test7() | |
print "\n-----test8-----" | |
test8() | |
print "\n-----test9-----" | |
test9() |
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