from sqlalchemy import create_engine
from sqlalchemy import Table, Column, Integer, String, ForeignKey, Sequence
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship


Base = declarative_base()


teachers_lessons = Table(
    "teachers_lessons",
    Base.metadata,
    Column("fk_teacher", Integer, ForeignKey("teachers.id")),
    Column("fk_lesson", Integer, ForeignKey("lessons.id")),
)


class Teacher(Base):
    __tablename__ = "teachers"

    id = Column("id", Integer, Sequence("teachers_id_seq"), primary_key=True)
    name = Column("name", String(50), nullable=False)

    lessons = relationship(
        "Lesson",
        backref="teachers",
        secondary=teachers_lessons
    )


class Lesson(Base):
    __tablename__ = "lessons"

    id = Column("id", Integer, Sequence("lessons_id_seq"), primary_key=True)
    name = Column("name", String(50), nullable=False)


engine = create_engine('rqlite+pyrqlite://localhost:4001/', echo=True)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)


if __name__ == "__main__":
    
    t2 = s.query(Teacher).filter_by(name='NEWNEW').first()
    t2.lessons.clear()
    s.commit()