python装饰器

'''
AOP之类装饰器
'''
#标准
def standard(class_):
class_.standard=class_
print(class_.name)
return class_
#非标准
def nonstandard(based_on):
def concrete_decorator(class_):
class_.standard=based_on
print(class_.name)
return class_
return concrete_decorator

class Unit:
factor=1.0
@classmethod
def value(class_,value):
if value is None:
return None
return value/class_.factor

@classmethod
def convert(class_,value):
if value is None:return None
return value*class_.factor

@standard
class INCH(Unit):
"""inch"""
name="in"

@nonstandard(INCH)
class FOOT(Unit):
"""foot"""
name='ft'
factor=1/12