python-装饰器学习示例

# -*- coding:utf-8 -*-

'''示例1: 最简单的函数,表示调用了两次'''
#
# def myfunc():
#     print("myfunc() called.")
#
# myfunc()
# myfunc()

# ------------------------------------------------------------------------------------------------------------

'''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()

# ------------------------------------------------------------------------------------------------------------

'''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()

# ------------------------------------------------------------------------------------------------------------

'''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()

# ------------------------------------------------------------------------------------------------------------

'''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)

# ------------------------------------------------------------------------------------------------------------

'''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)

# ------------------------------------------------------------------------------------------------------------

'''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()

# ------------------------------------------------------------------------------------------------------------

'''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()

# ------------------------------------------------------------------------------------------------------------

'''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

if __name__=="__main__":
a = example()
print '---------------------------------------------------'
a.myfunc()
print '---------------------------------------------------'
print(a.myfunc())
print '---------------------------------------------------'
print(a.myfunc2(1, 2))
print '---------------------------------------------------'
print(a.myfunc2(3, 4))