sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) 没有这样的表

Question

我对烧瓶很陌生，正在尝试自己建立一个博客，但遇到了 SQLite 操作错误的问题。我曾在 Github 和 Stackoverflow 上研究过类似的问题，但旧问题中的典型拼写错误或错误都没有发生在我身上。如果有人能帮助我，我将不胜感激，真的很棒，因为这个问题就像杀了我，已经花了我两天的时间，我感觉很糟糕。

在代码中，我定义了表名“users_table”并在开始时运行“db.create_all()”来创建表，但每次出现“no such table user_table”时都会出现错误提交更新用户信息。

这是我测试 SQLite 操作的方式：

(under /project) python3 manage.py shell
>>> u = User(email='foo@bar.com', username='foobar', password='player')
>>> db.create_all()
>>> db.session.add(u)
>>> db.session.commit()  # with following error message
Traceback (most recent call last):
  File "C:\...\Python\Python36-32\lib\site-packages\sqlalchemy\engine\base.py", line 1182, in _execute_context
  context)
  File "C:\...\Python\Python36-32\lib\site-packages\sqlalchemy\engine\default.py", line 470, in do_execute
  cursor.execute(statement, parameters)
sqlite3.OperationalError: no such table: users_table
...
...
  sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: users_table

我已将代码最小化为以下四个部分，可能会再次出现错误消息：

/project/app/__init__.py:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from config import config

db = SQLAlchemy()

def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    db.init_app(app)
    return app

/project/app/models.py:

import os
from flask_sqlalchemy import SQLAlchemy
from werkzeug.security import generate_password_hash
from flask import Flask

basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(basedir, 'data.sqlite')
app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
db = SQLAlchemy(app)


class User(db.Model):
    __tablename__ = 'users_table'
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(64), unique=True, index=True)
    username = db.Column(db.String(64), unique=True, index=True)
    password_hash = db.Column(db.String(128))

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

    @property
    def password(self):
        raise AttributeError('Password is not a readable attribute')

    @password.setter
    def password(self, password):
        self.password_hash = generate_password_hash(password)

项目/config.py：

import os
basedir = os.path.abspath(os.path.dirname(\__file__))

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY') or 'fhuaioe7832of67^&*T#oy93'
    SQLALCHEMY_COMMIT_ON_TEARDOWN = True

    @staticmethod
    def init_app(app):
        pass

class DevelopmentConfig(Config):
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(basedir, 'data.sqlite')

config = {
    'development': DevelopmentConfig,
    'default': DevelopmentConfig,
}

项目/manage.py：

import os
from app import create_app, db
from app.models import User
from flask_script import Manager, Shell

app = create_app(os.getenv('FLASK_CONFIG') or 'default')
manager = Manager(app)

def make_shell_context():
    return dict(app=app, db=db, User=User)

manager.add_command("shell", Shell(make_context=make_shell_context))


if __name__ == '__main__':
    manager.run()

Answer 1

非常简单的解决方案：在 app.py 或 main.py 中，您只需添加以下代码行即可解决此问题：

@app.before_first_request
def create_tables():
    db.create_all()

Answer 2

在您的情况下，需要将以下代码添加到 __init__.py 中：

from models import User, Role

@app.shell_context_processor
def make_shell_context():
    return dict(db=db, User=User, Role=Role)

然后你做你以前的工作，都是工作。

Answer 3

我刚刚完成了一个 Flask 应用程序的设置，并处理了这种问题。

我强烈怀疑这里的问题是您在__init__.py 中创建的db 实例不知道models.py 的内容，包括User 类。 __init__.py 中的 db 对象与您在 models.py 中创建的 db 完全不同。因此，当您在__init__.py 中运行db.create_all() 时，它会检查它所知道的表列表并且没有找到任何表。我遇到了这个确切的问题。

我发现模型（如 User）注册到模型类定义中列出的特定 db 对象（例如 class User(db.Model):）。

所以基本上我的理解是，解决此问题的方法是使用用于定义模型的 db 的同一实例运行 db.create_all()。换句话说，从models.py 中运行db.create_all()。

这是我的代码，您可以看看我是如何设置的：

app.py:

#!flask/bin/python
import os

from flask import Flask


class CustomFlask(Flask):
    jinja_options = Flask.jinja_options.copy()
    jinja_options.update(dict(
        variable_start_string='%%',  # Default is '{{', I'm changing this because Vue.js uses '{{' / '}}'
        variable_end_string='%%',
    ))
app = CustomFlask(__name__)

app.config['SECRET_KEY'] = 'hard to guess string'

import yaml
if os.environ['SERVER_ENVIRONMENT'] == 'PRODUCTION':
    config_filename = "production.yaml"
elif os.environ['SERVER_ENVIRONMENT'] == 'LOCAL':
    config_filename = "local.yaml"
else:
    config_filename = "local.yaml"

base_directory = path = os.path.dirname(os.path.realpath(__file__))

with open(base_directory + "/config/" + config_filename) as config_file:
    config = yaml.load(config_file)

db_config = config['database']
SQLALCHEMY_DATABASE_URI = "mysql+mysqlconnector://{username}:{password}@{hostname}/{databasename}".format(
    username=db_config['username'],
    password=db_config['password'],
    hostname=db_config['hostname'],
    databasename=db_config['databasename'],
)
app.config["SQLALCHEMY_DATABASE_URI"] = SQLALCHEMY_DATABASE_URI
app.config["SQLALCHEMY_POOL_RECYCLE"] = 299

from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy(app)
db.app = app


def clear_the_template_cache():
    app.jinja_env.cache = {}

app.before_request(clear_the_template_cache)

from flask_login import LoginManager
login_manager = LoginManager()
login_manager.init_app(app)


@login_manager.user_loader
def load_user(email):
    from models import User
    return User.query.filter_by(email=email).first()


if __name__ == '__main__':
    from routes import web_routes
    app.register_blueprint(web_routes)

    from api import api
    app.register_blueprint(api)

    # To get PyCharm's debugger to work, you need to have "debug=False, threaded=True"
    #app.run(debug=False, threaded=True)
    app.run(debug=True)

models.py:

from app import db

import datetime
from werkzeug.security import generate_password_hash, \
     check_password_hash


class Song(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(80))
    datetime_created = db.Column(db.DateTime, default=datetime.datetime.utcnow())
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    lines = db.relationship('Line', cascade="all,delete", backref=db.backref('song', lazy='joined'), lazy='dynamic')
    is_deleted = db.Column(db.Boolean, default=False)


class Line(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    song_id = db.Column(db.Integer, db.ForeignKey('song.id'))
    spans_of_time = db.relationship('SpanOfTime', cascade="all,delete", backref=db.backref('line', lazy='joined'), lazy='dynamic')


class SpanOfTime(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    line_id = db.Column(db.Integer, db.ForeignKey('line.id'))
    starting_64th = db.Column(db.Integer)  # I'm assuming the highest-granularity desired will be a 1/64th note-length.
    length = db.Column(db.Integer)  # I guess this'll be in 1/64th notes, so a 1/16th note will be '4'.
    content = db.Column(db.String(80))


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    email = db.Column(db.String(80), primary_key=True, unique=True)
    display_name = db.Column(db.String(80), default="A Rhymecraft User")
    password_hash = db.Column(db.String(200))
    datetime_subscription_valid_until = db.Column(db.DateTime, default=datetime.datetime.utcnow() - datetime.timedelta(days=1))
    datetime_joined = db.Column(db.DateTime, default=datetime.datetime.utcnow())
    songs = db.relationship('Song', cascade="all,delete", backref=db.backref('user', lazy='joined'), lazy='dynamic')

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

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

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password_hash, password)

    def is_authenticated(self):
        return True

    def is_active(self):
        return True

    def is_anonymous(self):
        return False

    def get_id(self):
        return str(self.email)


def init_db():
    db.create_all()

    # Create a test user
    new_user = User('a@a.com', 'aaaaaaaa')
    new_user.display_name = 'Nathan'
    db.session.add(new_user)
    db.session.commit()

    new_user.datetime_subscription_valid_until = datetime.datetime(2019, 1, 1)
    db.session.commit()


if __name__ == '__main__':
    init_db()