[英]Must two SQLAlchemy declarative models share the same declarative_base()?
[英]Share Declarative_Base (SQLAlchemy) with Singleton in Python
當一切都在一個文件中時,我可以正常運行SQLAlchemy。 我現在想把我的模型放到另一個文件中。
但是,這不起作用,因為我找不到共享基礎的方法。 我嘗試使用Singleton但它在model.py中是Null,並且從不在數據庫中創建模式。
我該怎么做才能解決這個問題?
我的文件(簡化版):
- /main/__init__.py
- /main/main.py
- /utils/__init__.py
- /utils/utils.py
- /model/__init__.py
- /model/model.py
main / main.py:
from model import User
from utils.utils import readConf,createSession,getBase
class Worker(threading.Thread):
def __init__(self, queue, session):
self.__queue = queue
threading.Thread.__init__(self)
self._stopevent = threading.Event( )
def run(self):
session.merge(User(queue.get()))
session.commit()
class Collector(threading.Thread):
def __init__(self, nom = ''):
threading.Thread.__init__(self)
self.nom = nom
self._stopevent = threading.Event( )
def run(self):
while not self._stopevent.isSet():
queue.put("Name")
if __name__ == '__main__':
conf = readConf("file.")
session = createSession(conf)
queue = Queue.Queue(0)
Worker(queue, session).start()
Collector("Start").start()
utils的/ utils.py
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.schema import MetaData
def createSession(conf):
schema = conf['bdd']['type'] + '://' + conf['bdd']['user'] + ':' + conf['bdd']['password'] + '@' + conf['bdd']['host'] + '/' + conf['bdd']['db']
engine = create_engine(schema, echo=True)
b = getBase("Utils")
b.set_base(declarative_base())
Base = b.get_base()
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
return session
class getBase(object):
__single = None # the one, true Singleton
__base = None
__text = None
__base = None
def __new__(cls, *args, **kwargs):
# Check to see if a __single exists already for this class
# Compare class types instead of just looking for None so
# that subclasses will create their own __single objects
if cls != type(cls.__single):
cls.__single = object.__new__(cls, *args, **kwargs)
__base = declarative_base()
return cls.__single
def __init__(self,name=None):
self.name = name
def get_base(self):
return self.__base
def set_base(self, value):
self.__base = value
模型/ model.py
from utils.utils import getBase
b = getBase("model")
b.set_base(declarative_base())
Base = b.get_base()
class User(Base):
__tablename__ = 'users'
def __init__(self, name):
self.screen_name = name
name_id = Column(Integer, primary_key=True, autoincrement=True)
screen_name = Column(BigInteger(), primary_key=True, nullable=False)
編輯@Lafaya
我更改了model/__init__.py
:
#!/usr/bin/python
Base = declarative_base()
然后我改變了model/model.py
:
from model import Base
class User(Base):
etc...
現在我無法從model.py導入Base(因為它由__init.py__
導入)。 但我需要參考Base!
Traceback (most recent call last):
File "../main/main.py", line 12, in <module>
from model.model import User
File "../model/model.py", line 3, in <module>
from model import Base
ImportError: cannot import name Base
在模型包的__init__.py
中寫入Base
。 然后你可以導入並使用它。
Jut將Base
放在model/__init__.py
。
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