在Flask中使用SQLAlchemy创建数据库 [英] Creating database with SQLAlchemy in Flask

问题描述

我想知道，在Flask中创建SQLAlchemy数据库需要做些什么.根据文档，我应该在Flask应用中创建模型，然后转到Python shell并只需使用 db.create_all()即可创建.但这是行不通的.

I'd like to know, what I need to do to create SQLAlchemy database in Flask. According to documentation I should create model in my Flask app and then go to the Python shell and just create this by using db.create_all(). But that doesn't work.

我的Flask应用程序:

My Flask app:

import os
import flask
import settings
from flask_sqlalchemy import SQLAlchemy

app = flask.Flask(__name__)
app.config['SESSION_TYPE'] = 'filesystem'
app.secret_key = os.urandom(24)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////database.db'
db = SQLAlchemy(app)
(...)

型号:

from app import db

class User(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    username = db.Column(db.String(15), unique = True)
    password = db.Column(db.String(15), unique = True)
    tasks = db.relationship('Task', backref='author', lazy='dynamic')

    def __init__(self, username, password):
        self.username = username
        self.password = password

class Task(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    scene = db.Column(db.String(140), nullable = False)
    state = db.Column(db.Integer(1), nullable = False)
    progress = db.Column(db.Integer(3), nullable = False)
    add_date = db.Column(db.DateTime, nullable = False)
    start_date = db.Column(db.DateTime, nullable = False)
    finish_date = db.Column(db.DateTime, nullable = False)
    rendered_scene = db.Column(db.String(140))
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

错误代码:

>>> from app import db
>>> db.create_all()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\site-packages\flask_sqlalchemy\__init__.py", line 895, in create_all
    self._execute_for_all_tables(app, bind, 'create_all')
  File "C:\Python27\lib\site-packages\flask_sqlalchemy\__init__.py", line 887, in _execute_for_all_tables
    op(bind=self.get_engine(app, bind), **extra)
  File "C:\Python27\lib\site-packages\sqlalchemy\sql\schema.py", line 3420, in create_all
    tables=tables)
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1727, in_run_visitor
    with self._optional_conn_ctx_manager(connection) as conn:
  File "C:\Python27\lib\contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1720, in_optional_conn_ctx_manager
    with self.contextual_connect() as conn:
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1910, incontextual_connect
    self.pool.connect(),
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 338, in connect
    return _ConnectionFairy._checkout(self)
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 645, in _checkout
    fairy = _ConnectionRecord.checkout(pool)
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 440, in checkout

    rec = pool._do_get()
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 1058, in _do_get

    return self._create_connection()
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 285, in _create_connection
    return _ConnectionRecord(self)
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 411, in __init__

    self.connection = self.__connect()
  File "C:\Python27\lib\site-packages\sqlalchemy\pool.py", line 539, in __connect
    connection = self.__pool._creator()
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\strategies.py", line 96, in connect
    connection_invalidated=invalidated
  File "C:\Python27\lib\site-packages\sqlalchemy\util\compat.py", line 199, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\strategies.py", line 90, in connect
    return dialect.connect(*cargs, **cparams)
  File "C:\Python27\lib\site-packages\sqlalchemy\engine\default.py", line 377, in connect
    return self.dbapi.connect(*cargs, **cparams)
sqlalchemy.exc.OperationalError: (OperationalError) unable to open database file
 None None

推荐答案

数据库uri中的/过多.格式为dialect+driver://user:pass@host:port/db_name.对于SQLite，db_name是数据库的路径.您已经指定了绝对路径/database.db，这意味着您正在尝试在文件系统的根目录中创建数据库.

You have one too many / in the database uri. The format is dialect+driver://user:pass@host:port/db_name. With SQLite, db_name is the path to the database. You've specified the absolute path /database.db, which means you're trying to create the database in the filesystem's root directory.

使用sqlite:///database.db(相对路径)将在(相对于)当前工作目录中创建数据库.

Using sqlite:///database.db (a relative path) will create the database in (relative to) the current working directory.

您可能要指定一个绝对路径，但要根据项目位置进行构建，因为您可以从另一个文件夹运行该应用程序.假设您要在与应用设置代码相同的目录中创建数据库，请构建相对于__file__的路径.

You probably want to specify an absolute path, but build it based on the project location, since you could run the application from another folder. Assuming you want to create the db in the same directory as the app setup code, build a path relative to __file__.

db_path = os.path.join(os.path.dirname(__file__), 'app.db')
db_uri = 'sqlite:///{}'.format(db_path)
app.config['SQLALCHEMY_DATABASE_URI'] = db_uri

这篇关于在Flask中使用SQLAlchemy创建数据库的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！