sqlalchemy orm-从数据库获取表定义

Question

Sqlalchemy，是否有一种直接创建表定义类的方法，BeaCause表已在DB中存在，大多数文档都告诉我，将其定义进行人工制作。

Base = declarative_base()

# ORM defininition
class Dep(Base):
    __tablename__='dep'
    id=Column(Integer,primary_key=True,autoincrement=True)
    dname=Column(String(64),nullable=False,index=True)

# Add new obs
session = sessionMaker()
row_obj=Dep(dname='saleman') 
session.add(row_obj)

Answer 1

有在sqlalchemy 中。

我将在此处放置受文档启发的示例。

1。给班级

from sqlalchemy import Table, create_engine
from sqlalchemy.orm import declarative_base

Base = declarative_base()  # same declarative_base() as usual

engine = create_engine("sqlite:///mydatabase.db")  # get your engine

class User(Base):
    __table__ = Table("user", Base.metadata, autoload_with=engine)

2。用 automap扩展

from sqlalchemy import create_engine
from sqlalchemy.ext.automap import automap_base

Base = automap_base()  # rather than declarative_base()

engine = create_engine("sqlite:///mydatabase.db")  # get your engine

Base.prepare(autoload_with=engine)  # reflect the tables and classes

User = Base.classes.user  # retrieve classes from table name

3。从 deferredreflection扩展

from sqlalchemy.ext.declarative import DeferredReflection
from sqlalchemy.orm import declarative_base

Base = declarative_base()  # same declarative_base() as usual

class User(DeferredReflection, Base):  # define your class
    __tablename__ = "user"

engine = create_engine("sqlite:///mydatabase.db")  # get your engine

User.prepare(engine)  # reflect the table and attributes

两个第一个示例需要引擎来创建类，这可能会带来不方便的测试等，因此，我因此更喜欢让我可以在不同地方定义的第三个，但三个都可以使用。