先贴错误：

sqlalchemy.exc.ArgumentError: Mapper Mapper|Base|base could not assemble any primary key columns for mapped table 'base'

base.py 

from sqlalchemy import Column,SmallInteger
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class Base(db.Model):
    status = Column(SmallInteger, default=1)

gift.py

from sqlalchemy import Column,Integer,String,Float,Boolean,ForeignKey,SmallInteger
from sqlalchemy.orm import relationship

from app.models.base import Base


class Gift(Base):
    id = Column(Integer, primary_key=True)
    user = relationship('User')
    uid = Column(Integer, ForeignKey('user.id'))
    isbn = Column(String(15),nullable=False)
    #book = relationship('Book')
    #bid = Column(Integer, ForeignKey('book.id'))
    launched = Column(Boolean,default=False)

同样的 book.py和user.py也继承了base.py 。运行的时候报上面的错误