def my_decorator(function):
def _my_decorator(*args, **kw):
#在调用实际函数之前做些填充工作
res = function(*args, **kw)
#做完某些填充工作之后
return res
#返回子函数
return _my_decorator
当装饰器需要参数时，必须使用第二级封装。
def my_decorator(arg1, arg2):
def _my_decorator(function):
def __my_decorator(*args, **kw):
res = function()
return res
return __my_decorator
return _my_decorator
引用
因为装饰器在模块第一次被读取时由解释程序装入，所以它们的使用必须受限于总体上可以应用的封装器。如果装饰器与方法的类或所增强的函数签名绑定，它应该被重构为常规的可调用对象，从而避免复杂性。在任何情况下，当装饰器处理API时，一个好的方法是将它们聚集在一个易于维护的模块中。
参数检查：
def check_param_isvalid():
def check(method):
def check_param(*args,**kwargs):
for a in args:
assert isinstance(a, int),"arg %r does not match %s" % (a,int)
assert a > 100000,"arg %r must gt 100000" % a
return method(*args, **kwargs)
return check_param
return check
@check_param_isvalid()
def foo(*args):
print args
foo(200000,500000)
缓存：
import time
import hashlib
import pickle
cache = {}
def is_obsolete(entry, duration):
return time.time() - entry['time'] > duration
def computer_key(function, args, kw):
key = pickle.dumps((function.func_name, args, kw))
return hashlib.sha1(key).hexdigest()
def memoize(duration=30):
def _memoize(function):
def __memoize(*args, **kw):
key = computer_key(function, args, kw)
if key in cache and not is_obsolete(cache[key], duration):
print 'wo got a winner'
return cache[key]['value']
result = function(*args, **kw)
cache[key] = {'value':result,'time':time.time()}
return result
return __memoize
return _memoize
@memoize()
def very_complex_stuff(a,b):
return a + b
print very_complex_stuff(2,2)
代理：
class User(object):
def __init__(self, roles):
self.roles = roles
class Unauthorized(Exception):
pass
def protect(role):
def _protect(function):
def __protect(*args, **kw):
user = globals().get('user')
if user is None or role not in user.roles:
raise Unauthorized("I won't tell you")
return function(*args, **kw)
return __protect
return _protect
tarek = User(('admin', 'user'))
bill = User(('user',))
class MySecrets(object):
@protect('admin')
def waffle_recipe(self):
print 'use tons of butter!'
these_are = MySecrets()
user = tarek
these_are.waffle_recipe()
user = bill
these_are.waffle_recipe()
上下文提供者：
from threading import RLock
lock = RLock()
def synchronized(function):
def _synchronized(*args, **kw):
lock.acquire()
try:
return function(*args, **kw)
finally:
lock.release()
return _synchronized
@synchronized
def thread_safe():
print 'haha'
thread_safe()
补充：http://2057.iteye.com/blog/1838398
参考资料：
Python高级编程
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2013-10-15 22:59
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