SQLAlchemy继承不起作用

  • Z时代
  • 2024-01-10
  • 分类：问答

我正在使用Flask和SQLAlchemy。我使用了自己的抽象基类和继承。当我尝试在python shell中使用模型时，出现以下错误：

>>> from schedule.models import Task
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/teelf/projects/schedule/server/schedule/models.py", line 14, in <module>
    class User(Base):
  File "/home/teelf/projects/schedule/server/venv/lib/python3.4/site-packages/flask_sqlalchemy/__init__.py", line 536, in __init__
    DeclarativeMeta.__init__(self, name, bases, d)
  File "/home/teelf/projects/schedule/server/venv/lib/python3.4/site-packages/sqlalchemy/ext/declarative/api.py", line 55, in __init__
    _as_declarative(cls, classname, cls.__dict__)
  File "/home/teelf/projects/schedule/server/venv/lib/python3.4/site-packages/sqlalchemy/ext/declarative/base.py", line 254, in _as_declarative
    **table_kw)
  File "/home/teelf/projects/schedule/server/venv/lib/python3.4/site-packages/sqlalchemy/sql/schema.py", line 393, in __new__
    "existing Table object." % key)
sqlalchemy.exc.InvalidRequestError: Table 'user' is already defined for this MetaData instance.  Specify 'extend_existing=True' to redefine options and columns
 on an existing Table object.

我该如何解决？

码：

manage.py：

#!/usr/bin/env python
import os, sys
sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
from flask.ext.migrate import Migrate, MigrateCommand
from flask.ext.script import Manager
from server import create_app
from database import db
app = create_app("config")
migrate = Migrate(app, db)
manager = Manager(app)
manager.add_command("db", MigrateCommand)
if __name__ == "__main__":
    manager.run()

.py：

from flask import Flask
from flask.ext.login import LoginManager
from database import db
from api import api
from server.schedule.controllers import mod_schedule
def create_app(config):
    # initialize Flask
    app = Flask(__name__)
    # load configuration file
    app.config.from_object(config)
    # initialize database
    db.init_app(app)
    api.init_app(app)
    # initialize flask-login
    login_manager = LoginManager(app)
    # register blueprints
    app.register_blueprint(mod_schedule)
    return app

database.py：

from flask.ext.sqlalchemy import SQLAlchemy
db = SQLAlchemy()

models.py：

from sqlalchemy.dialects.postgresql import UUID
from database import db
class Base(db.Model):
    __abstract__ = True
    id = db.Column(UUID, primary_key=True)
class User(Base):
    __tablename__ = "user"
    username = db.Column(db.String)
    password = db.Column(db.String)
    first_name = db.Column(db.String)
    last_name = db.Column(db.String)
    authenticated = db.Column(db.Boolean, default=False)
    def __init__(self, first_name, last_name, username):
        self.first_name = first_name
        self.last_name = last_name
        self.username = username
    def is_active(self):
        """ All users are active """
        return True
    def get_id(self):
        return self.username
    def is_authenticated(self):
        return self.authenticated
    def is_anonymous(self):
        """ Anonymous users are not supported"""
        return False

controllers.py：

from flask import Blueprint
from flask.ext.restful import reqparse, Resource
from api import api
from server.schedule.models import User
mod_schedule = Blueprint("schedule",  __name__, url_prefix="/schedule")
class Task(Resource):
    def put(self):
        pass
    def get(self):
        pass
    def delete(self):
        pass
api.add_resource(Task, "/tasks/<int:id>", endpoint="task")

回答：

尝试添加

 __table_args__ = {'extend_existing': True}

在你的User类下__tablename__=

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