在sqlalchemy的一般解释中,有一些使用全局变量的基本设置。但是如何避免这些全球性问题呢?
这是基本设置:
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
databaseName = 'fixedDBName.db'
engine = create_engine('sqlite:///' + databaseName, echo=True)
Base = declarative_base()
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
from sqlalchemy import Column, Integer, String
class User(declarative_base()):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
fullname = Column(String)
nickname = Column(String)
def __repr__(self):
return "<User(name='%s', fullname='%s', nickname='%s')>" % (
self.name, self.fullname, self.nickname)
#Now you can create a session
Session = sessionmaker(bind=engine)
session = Session()
现在,这给我提出了一些问题:
我可以在需要时启动数据库连接,然后关闭它,然后在再次需要时启动新的数据库连接吗?
你是如何在项目中使用它的?
是否将与数据库有关的所有内容都打包到类中。这样您就可以创建该函数的实例了吗?像这样:
class sqlcon():
def __init__(self, databaseName):
self.engine = create_engine('sqlite:///' + databaseName, echo=True)
self.Session = sessionmaker(bind=self.engine)
Base = declarative_base()
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
fullname = Column(String)
nickname = Column(String)
def __repr__(self):
return "<User(name='%s', fullname='%s', nickname='%s')>" % (
self.name, self.fullname, self.nickname)
def createTables(self):
Base.metadata.create_all(self.engine) #doesn´t work - Base is not Defined
Base.metadata.create_all(self.engine) #doesn´t work - self is not Defined
或者你把这个装在一个函数里吗:
def sqlcon(databaseName):
engine = create_engine('sqlite:///' + databaseName, echo=True)
Base = declarative_base()
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
fullname = Column(String)
nickname = Column(String)
def __repr__(self):
return "<User(name='%s', fullname='%s', nickname='%s')>" % (
self.name, self.fullname, self.nickname)
Base.metadata.create_all(engine)
databaseName = "test_3.db"
alchemy = sqlcon(databaseName)
但是,如何创建会话以及如何访问类User?
在这里,我需要朝着正确的方向推动:/
答案很简单:Base只是保持全局性!
在github上的所有例子中,你都是这样发现的。
在我的情况下是:
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
Base = declarative_base()
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String)
fullname = Column(String)
nickname = Column(String)
def __repr__(self):
return "<User(name='%s', fullname='%s', nickname='%s')>" % (
self.name, self.fullname, self.nickname)
if __name__ == "__main__":
engine = create_engine("sqlite://")
Base.metadata.create_all(engine)
session = Session(engine)