pythonのsqlalchemy多对多关系

现在来设计一个能描述“图书”与“作者”的关系的表结构，需求是

1. 一本书可以有好几个作者一起出版
2. 一个作者可以写好几本书

#!/usr/bin/env python
from sqlalchemy import Table,Column,Integer,String,DATE,ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker


engine = create_engine("mysql+pymysql://root:root@localhost/testuser?charset=utf8",encoding="utf-8",echo=True)
# 生成orm基类
Base = declarative_base()


# 创建表映射
book_m2m_author = Table("book_m2m_author",Base.metadata,
                        Column("book_id",Integer,ForeignKey("books.id")),
                        Column("author_id",Integer,ForeignKey("authors.id")))

class Book(Base):
    __tablename__ = "books"
    id = Column(Integer,primary_key=True)
    name = Column(String(64))
    pub_date = Column(DATE)
    authors = relationship("Author",secondary=book_m2m_author,backref="books")

    def __repr__(self):
        return self.name

class Author(Base):
    __tablename__ = "authors"
    id = Column(Integer,primary_key=True)
    name = Column(String(32))

    def __repr__(self):
        return self.name

# 构建表结构
Base.metadata.create_all(engine)

#!/usr/bin/env python
from day12 import orm_m2m_fk
from sqlalchemy.orm import sessionmaker

# 创建与数据库会话实例。
session_class = sessionmaker(bind=orm_m2m_fk.engine)

# 生成session实例
session = session_class()

# b1 = orm_m2m_fk.Book(name="Java从入门到精通",pub_date="2018-08-08")
# b2 = orm_m2m_fk.Book(name="Python从入门到精通",pub_date="2018-08-08")
# b3 = orm_m2m_fk.Book(name="JavaScript从入门到精通",pub_date="2018-08-08")
# b4 = orm_m2m_fk.Book(name=".Net从入门到精通",pub_date="2018-08-08")
#
#
# a1 = orm_m2m_fk.Author(name="Jerry")
# a2 = orm_m2m_fk.Author(name="Tom")
# a3 = orm_m2m_fk.Author(name="Jack")
#
# b1.authors = [a1,a3]
#
# b3.authors = [a1,a2,a3]
#
# b2.authors = [a2,a3]
#
# b4.authors = [a1]
#
# session.add_all([b1,b2,b3,b4,a1,a2,a3])

a = session.query(orm_m2m_fk.Author).filter(orm_m2m_fk.Author.name=="Jerry").first()
print(a.books)
session.commit()

C:UsersAdministratorAppDataLocalProgramsPythonPython37python.exe D:/PythonStudy/charm/01/day12/orm_m2m_aip.py
2018-09-20 09:22:14,652 INFO sqlalchemy.engine.base.Engine SHOW VARIABLES LIKE 'sql_mode'
2018-09-20 09:22:14,652 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,656 INFO sqlalchemy.engine.base.Engine SELECT DATABASE()
2018-09-20 09:22:14,656 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,656 INFO sqlalchemy.engine.base.Engine show collation where `Charset` = 'utf8mb4' and `Collation` = 'utf8mb4_bin'
2018-09-20 09:22:14,656 INFO sqlalchemy.engine.base.Engine {}
C:UsersAdministratorAppDataLocalProgramsPythonPython37libsite-packagespymysqlcursors.py:170: Warning: (1366, "Incorrect string value: '\xD6\xD0\xB9\xFA\xB1\xEA...' for column 'VARIABLE_VALUE' at row 484")
  result = self._query(query)
2018-09-20 09:22:14,658 INFO sqlalchemy.engine.base.Engine SELECT CAST('test plain returns' AS CHAR(60)) AS anon_1
2018-09-20 09:22:14,658 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,658 INFO sqlalchemy.engine.base.Engine SELECT CAST('test unicode returns' AS CHAR(60)) AS anon_1
2018-09-20 09:22:14,658 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,659 INFO sqlalchemy.engine.base.Engine SELECT CAST('test collated returns' AS CHAR CHARACTER SET utf8mb4) COLLATE utf8mb4_bin AS anon_1
2018-09-20 09:22:14,659 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,660 INFO sqlalchemy.engine.base.Engine DESCRIBE `book_m2m_author`
2018-09-20 09:22:14,660 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,661 INFO sqlalchemy.engine.base.Engine DESCRIBE `books`
2018-09-20 09:22:14,661 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,663 INFO sqlalchemy.engine.base.Engine DESCRIBE `authors`
2018-09-20 09:22:14,663 INFO sqlalchemy.engine.base.Engine {}
2018-09-20 09:22:14,668 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2018-09-20 09:22:14,668 INFO sqlalchemy.engine.base.Engine SELECT authors.id AS authors_id, authors.name AS authors_name 
FROM authors 
WHERE authors.name = %(name_1)s 
 LIMIT %(param_1)s
2018-09-20 09:22:14,669 INFO sqlalchemy.engine.base.Engine {'name_1': 'Jerry', 'param_1': 1}
2018-09-20 09:22:14,670 INFO sqlalchemy.engine.base.Engine SELECT books.id AS books_id, books.name AS books_name, books.pub_date AS books_pub_date 
FROM books, book_m2m_author 
WHERE %(param_1)s = book_m2m_author.author_id AND books.id = book_m2m_author.book_id
2018-09-20 09:22:14,670 INFO sqlalchemy.engine.base.Engine {'param_1': 1}
[Java从入门到精通, JavaScript从入门到精通, .Net从入门到精通]
2018-09-20 09:22:14,675 INFO sqlalchemy.engine.base.Engine COMMIT

Process finished with exit code 0