python - SQLAlchemy 告诉我 "AttributeError: type object ' User' 没有属性 'columns' "

Question

我正在使用 python+Flask+SQLAlchemy 构建一个小项目，我制作了一个模型文件如下:

################# start of models.py #####################
from sqlalchemy import Column, Integer, String, Sequence, Date, DateTime, ForeignKey
from sqlalchemy.orm import relationship, backref
from dk.database import Base
import datetime

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, Sequence('seq_user_id'), primary_key=True)
    name = Column(String(50), unique=True, index = True, nullable = False)
    email = Column(String(120), unique=True, index = True, nullable = False)
    password = Column(String(128), nullable = False)

    def __init__(self, name, email, password):
        self.name = name
        self.email = email
        self.password = password

    def __repr__(self):
        return '<User %r>' % (self.name)

class Session(Base):
    __tablename__ = 'session'
    id = Column(String(128), primary_key = True, nullable = False)
    user_name = Column(String(30), nullable = False)
    user_id = Column(Integer, ForeignKey('users.id'))
    user = relationship('User', backref=backref('session', lazy='dynamic'))

    def __repr__(self):
        return '<Session %r>' % (self.id)
################# end of models.py #####################

我构建了一个初始文件:

################# start of __init__.py #################
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config.from_object('config') #load database config information
db = SQLAlchemy(app)
################# end of __init__.py #################

当我在脚本中运行“init_db()”时，构建数据库的表成功。但是当我想查看 SQL 脚本然后我在脚本中运行“print CreateTable(User)”时，系统显示以下错误:

  File "/home/jacky/flaskcode/venv/lib/python2.6/site-packages/sqlalchemy/schema.py", line 3361, in __init__
    for column in element.columns
AttributeError: type object 'User' has no attribute 'columns'

我不知道如何解决这个问题!

Answer 1

您需要为CreateTable()传入一个Table对象:

CreateTable(User.__table__)

但是如果您想查看 SQLAlchemy 发出的 SQL 语句，最好通过设置 echo=True when creating the connection 来打开回显。 .

Flask SQLAlchemy 集成层支持SQLALCHEMY_ECHO option设置该标志。