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

Question

刚接触flask，想自己建个博客，遇到sqlite操作错误的问题。我在 Github 和 Stackoverflow 上研究过类似的问题，但我没有遇到过旧问题中的典型拼写错误或错误。如果有人能帮助我，我将不胜感激，这真的很棒，因为这个问题就像要了我的命，已经花了我两天时间，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，但是每次提交时都会出现“no such table user_table”错误更新用户信息。

这是我测试 SQLite 操作的方式：

 (under /project) python3 manage.py shell
>>> u = User(email='[e-mail]', 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，这些部分可能会再次出现错误消息：

/项目/应用程序/__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

/项目/应用程序/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/管理.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()

原文由 nonemaw 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

我刚刚完成了 Flask 应用程序的设置，并处理了此类问题。

I strongly suspect the problem here is that the instance of db that you are creating in __init__.py is unaware of the contents of models.py , including the User 类。 The db object in __init__.py is a totally separate object from the db you are creating in models.py .因此，当您在 db.create_all() __init__.py ，它正在检查它知道的表列表，但没有找到任何表。我遇到了这个确切的问题。

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

所以基本上我的理解是解决这个问题的方法是运行 db.create_all() 使用用于定义模型的 db 的相同实例。换句话说，从 --- 运行 db.create_all() models.py 。

这是我的代码，您可以看到我是如何设置它的：

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('[e-mail]', '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()

原文由 Nathan Wailes 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

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

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

原文由 Abbas Jafari 发布，翻译遵循 CC BY-SA 4.0 许可协议