property裝飾器的實現 & 描述器的深入思考
阿新 • • 發佈:2020-10-08
class Property:
def __init__(self,fget=None,fset=None,fdel=None):
self.fget=fget
self.fset=fset
self.fdel=fdel
def __repr__(self):
return 'self: {} fget: {} fset: {} fdel: {}'.format(id(self),self.fget,self.fset,self.fdel)
def __get__(self,instance,owner):
if instance is None:
return self
return self.fget(instance)
def __set__(self,instance,value):
if self.fset is None: # 未設定setter時,進行屬性設定,丟擲異常
raise AttributeError('{} has no setter set'.format(instance.__class__.__name__))
if instance is None: # class call
return self
self.fset(instance,value)
def __delete__(self,instance):
if self.fdel is None: # 未設定deleter時,刪除屬性,拋異常
raise AttributeError('{} has no deleter set'.format(instance.__class__.__name__))
if instance is None: # class call
return self
self.fdel(instance)
def setter(self,fset):
print(self.fget.__name__,fset.__name__)
if self.fget.__name__ != fset.__name__: # setter 和 getter裝飾的函式名字不同時,建立新描述器
return Property(fset=fset)
self.fset=fset
return self
def deleter(self,fdel):
print(self.fset.__name__,fdel.__name__)
if fdel.__name__ != self.fset.__name__: # deleter 和 setter裝飾的函式名字不同時,建立新描述器
return Property(fdel=fdel)
self.fdel=fdel
return self
class B:
def __init__(self,data):
self._data=data
@Property # datum1=Property(datum)
def datum1(self):
return self._data
@datum1.setter # datum2=datume1.setter(datum2)
def datum2(self,value):
self._data=value
@datum2.deleter # datum3=datum2.deleter(datum3)
def datum3(self):
del self._data
print(B.datum1)
print(B.datum2)
print(B.datum3)
b=B(22)
print(b.datum1)
b.datum2=33
print(b.datum1)
print(b.__dict__)
del b.datum3
print(b.__dict__)