sqlalchemy - How to use descriptors in sqlachemy.orm.synonym -

i have code working fine:

def get_timestamp(ts):     return datetime.utcfromtimestamp(ts)  def set_timestamp(dt):     return time.mktime(dt.timetuple())  class group(base):     __tablename__ = 'group'     _created = column('created', integer, nullable=false)      @property     def created(self):         return get_timestamp(self._created)     @created.setter     def created(self, value):         self._created = set_timestamp(value) 

i want code this, it's not working:

created = synonym('_created',                   descriptor=property(get_timestamp,                                       set_created)) 

because passed in self 1st param.

i'd use get_timestamp , set_timestamp across project of cause. i'm not going make them methods of class stand alone function.

how can achieve this?

edit: take option2, , still open other answers.

option-1: code below should work (you not need have class in order define self):

def pget_timestamp(self):     return datetime.utcfromtimestamp(self._created)  def pset_timestamp(self, dt):     self._created = time.mktime(dt.timetuple())  class group(base):     __tablename__ = 'group'     id = column(integer, primary_key=true)     _created = column('created', integer, nullable=false)      created = synonym(_created,             descriptor=property(pget_timestamp, pset_timestamp),             ) 

option-2: if need same on many classes, leverage mixins

from sqlalchemy.ext.declarative import declared_attr class _createdmixin(object):     _created = column('created', integer, nullable=false)      def pget_timestamp(self):         return datetime.utcfromtimestamp(self._created)      def pset_timestamp(self, dt):         self._created = time.mktime(dt.timetuple())      @declared_attr     def created(cls):         return synonym('_created',             descriptor=property(cls.pget_timestamp, cls.pset_timestamp),             )   class group(_createdmixin, base):     # @note: adding *_createdmixin* bases defines both column , synonym     __tablename__ = 'group'     id = column(integer, primary_key=true) 

alternatively, if all classes, make _createdmixin base class models:

base = declarative_base(engine, cls=_createdmixin) class group(base):     __tablename__ = 'group'     id = column(integer, primary_key=true) 

option-3: of above using hybrid attributes

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note: make set/get functions in-sync: either both or none use utc-enabled functionality. (unless in utc-0) setting 1 value created not return same 1 back.