Python 具有来自其他表的多个外键的SQLalchemy表

我正在尝试学习

sqlalchemy

，但在创建一个对象时有点困惑，该对象将进入一个表，该表具有其他两个表的外键。下面是一个简单的例子，说明我正在尝试做什么。我正在制作一个配方数据库，有三个表：

配方

，

配料

，和

配方_配料

<代码>配方\配料将配料链接到配方。我有这样的积累：

from sqlalchemy import create_engine, Column, Integer, Text, ForeignKey
from sqlalchemy.orm import relationship, scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine(u'sqlite:///:memory:', echo=True)
session = scoped_session(sessionmaker(bind=engine))
Base = declarative_base()

class Recipe(Base):
    __tablename__ = 'recipes'
    id = Column(Integer, primary_key=True)
    name = Column(Text)

    recipe_ingredient = relationship('RecipeIngredient', back_populates='recipe')

class Ingredient(Base):
    __tablename__ = 'ingredients'
    id = Column(Integer, primary_key=True)
    name = Column(Text)

    recipe_ingredient = relationship('RecipeIngredient', back_populates='ingredient')

class RecipeIngredient(Base):
    __tablename__ = 'recipe_ingredients'
    id = Column(Integer, primary_key=True)
    recipe_id = Column(Integer, ForeignKey('recipes.id'))
    ingredient_id = Column(Integer, ForeignKey('ingredients.id'))

    recipe = relationship('Recipe', back_populates='recipe_ingredient')
    ingredient = relationship('Ingredient', back_populates='recipe_ingredient')

ham = Ingredient(name='cereal')
bread = Ingredient(name='milk')
cheese = Ingredient(name='cheese')
sandwich = Recipe(name='ham and cheese')
# Now I'm not sure how to link theses
link1 = RecipeIngredient(recipe_id=sandwich.id, ingredient_id=ham.id)
link2 = RecipeIngredient(recipe_id=sandwich.id, ingredient_id=bread.id)
link3 = RecipeIngredient(recipe_id=sandwich.id, ingredient_id=cheese.id)

session.add_all([ham, bread, cheese, sandwich, link1, link2, link3])
session.commit()

---

这不起作用，因为

RecipeingCredit

对象。我怎样才能像这样链接外键来创建这些对象

使用ForeignKeyConstraint和ForeignKey的组合

    from sqlalchemy import ForeignKeyConstraint

    class RecipeIngredient(Base):
        ...
        recipe_id = Column(Integer, ForeinKey('recipes.id'))
        ingredient_id = Column(Integer)

        __table_args__ = (
        ForeignKeyConstraint(
            ["ingrediants_id"],
            ["ingredients.id"]
        ),)
        ...

---

由于这是一个重复标记，我不能留下一个答案。我所做的只是在类定义之后（即'ham='行之前）添加

Base.metadata.create_All（engine）

，它就成功了。